A microscopic dynamic light scattering measurement system is proposed to meet the demands of detecting the particle size of minute biological samples. Traditional dynamic light scattering techniques typically require samples at the milliliter level, making them unsuitable for detecting minute biological samples. To address this issue, a microscopic dynamic light scattering system was designed that integrates conventional microscopy and dynamic light scattering technologies. By combining these two techniques, the sample volume was successfully reduced to tens of microliters, achieving a two-order-of-magnitude improvement and significantly reducing sample consumption, thus meeting the laboratory's requirements for trace biological detection. To validate the feasibility of the system, different materials and sizes of nanoparticles as well as biological extracellular vesicle samples were evaluated. The experimental results showed that the measurement size errors for polystyrene microspheres particles at 60nm and exosomes particles at 208.6nm were 1.5% and -3.4%, respectively, which were in good agreement with the actual size, confirming the practicality of the system in practical applications.