To address the specific requirements of particle image velocimetry systems in microscopic imaging applications, particularly focusing on the challenges encountered when commercial microscopes fail to meet the demands for long working distance, high resolution, and integrated design, a novel 30×fluorescence detection microscope with a long-working-distance apochromatic objective lens specifically tailored for micro-PIV measurements is developed.The design process employs refractive design principles and an infinity-corrected structure to ensure high-quality imaging across a broad visible light spectrum (400~800 nm). The illumination system is designed to provide uniform and stable light, which is critical for capturing high-quality fluorescence images. The imaging components, including the objective lens, tube lens, and filters, are meticulously arranged to achieve a compact and user-friendly system. The optical design has been optimized to minimize various aberrations, including chromatic and spherical aberrations, ensuring that the overall imaging performance approaches the diffraction limit. Methods for increasing the working distance and techniques for apochromatic correction are proposed. The main way to increase the working distance is to adjust the focal length and interval of the negative light group and the positive light group. The method of apochromatism is mainly replacing glass materials and combining them. After optimization, a numerical aperture of 0.35, a working distance of 17.3 mm, and a microscopic objective with a magnification of 30 times were formed, which exceeded the limitations of conventional microscopic objectives. Additionally, the mechanical design of the microscope emphasizes robustness and ease of use, with the entire system weighing approximately 17.29 kg and measuring 360 mm×300 mm×300 mm. The entire microscope system is designed to be portable and lightweight, enabling remote operation capabilities. It features excellent sealing properties, allowing it to be deployed in complex environments while minimizing stray light interference. Additionally, the displacement stage provides a user-friendly interface for observing various microfluidic channels, enhancing the system's versatility and usability in diverse experimental settings.Upon completion of the optical and mechanical designs, the optical lens and mechanical structure of the complete system are manufactured. After assembling and building, the system undergoes rigorous testing and evaluation. Initial tests involve imaging a USAF standard resolution target to assess the optical resolution of the microscopic system. The results demonstrate that the microscope achieves a resolution greater than 228 lp/mm, corresponding to a line width of 2.2 μm, which meets the required specifications for micro-PIV applications. Subsequently, the system is employed in micro-PIV experiments on a microfluidic chip containing fluorescent particles with a velocity of nearly 1 m/s. The particles are illuminated with a 532 nm laser, and a double-exposure camera captured the resulting fluorescence at 613 nm through a 550 nm high-pass filter. The captured images display clear and distinct particle images, even for particles as small as 1 μm in diameter, confirming the high resolution and sensitivity of the system. These particle images are then processed using a Fourier transform-based cross-correlation algorithm to analyze the velocity field within the microfluidic chip. The algorithm calculates the displacement of particles between two consecutive frames and derives the velocity vectors based on the time interval and magnification factor. The velocity distribution obtained from the experiments shows excellent agreement with theoretical simulations, with a deviation of less than 6% between the measured velocities and the simulated values.The optical and mechanical design of the proposed microscope meets the stringent requirements for high resolution, long working distance, and integrated functionality. The experimental results validate the feasibility and effectiveness of the system, demonstrating its capability to provide clear and accurate particle images and reliable velocity measurements. This work can offer a valuable reference for the development of specialized microscopic imaging systems.