A significant hurdle in current deep-sea microbial research remains the inability to capture these microbes in their natural habitat. Optical tweezers, with their non-contact, low-damage, and highly precise capabilities, present an ideal solution for capturing and manipulating microorganisms in liquid environments, showing promise in capturing deep-sea microbes. However, existing research on optical tweezers primarily focuses on ideal mediums such as pure water and air, with few studies exploring their application and the alteration of trapping force characteristics in the deep-sea environment.In order to address the challenge of accurately capturing and collecting deep-sea microorganisms, this paper presents a designed optical tweezers acquisition system tailored for deep-sea environments. The system incorporates an optical tweezers module, a microfluidic chip, and a pressure-resistant cover, facilitating the in-situ capture and sorting of deep-sea microorganisms. In examining the alteration of trapping force in optical tweezers in deep-sea conditions compared to pure water, this study initially outlines the principle and methodology for calculating trapping force using the T-matrix method. Subsequently, it investigates the factors influencing optical tweezers' trapping power in the deep-sea environment, including changes in seawater's refractive index and light wave attenuation. To achieve this, a refractive index model for seawater at 1.5 km north latitude of 18° in the South China Sea is established, and the attenuation coefficient of seawater to light waves is estimated based on prior research data. Furthermore, under consistent experimental parameters, the study employs the T-matrix method to calculate the trapping force of Gaussian optical tweezers in both deep-sea conditions and pure water. This aims to capture spherical microorganisms of varying sizes and refractive indices, assessing the decrease in trapping force of optical tweezers in the deep-sea compared to pure water.Our experimental findings reveal that the shape of the dispersion curve of seawater at 1.5 km is almost the same as that of pure water on land, indicating a relatively gentle curve and an Abbe number exceeding 55, indicating minimal dispersion in seawater. Notably, compared to pure water, the refractive index of seawater is slightly higher, measuring 1.34 at a wavelength of 785 nm, a marginal increase from pure water's 1.33. At this juncture, the attenuation coefficient of seawater stands at approximately 2.3 m^-1, resulting in a 92% transmittance through a 3.5 mm thick seawater layer. The study calculates the optical forces exerted by optical tweezers on spherical microorganisms with radii of 1 μm, 3 μm, 5 μm, and 10 μm in both the 1.5 km deep-sea environment and a pure water environment, with refractive indices of 1.35, 1.4, and 1.5, respectively. The findings indicate an average decrease of approximately 25% in maximum axial capturing force and about 20% in maximum transverse capturing force in the deep-sea environment compared to pure water on land. This emphasizes the greater influence of the increase in the medium's refractive index surrounding the target on the axial capturing force than on the transverse capturing force. Notably, these optical tweezers experiments employed the same laser power. Considering the greater attenuation of laser power in the deep-sea compared to pure water, the maximum trapping force of optical tweezers is proportional to the attenuation amplitude of the laser power.In summary, this study applies optical tweezers technology to in-situ capture deep-sea microorganisms, extending the technology's application domain. Additionally, it represents a comprehensive exploration of optical tweezers' functionality in a distinctive and demanding environment. These findings could serve as a valuable reference for future experiments developing deep-sea microbial sorting equipment utilizing optical tweezers technology.