Studying the influence of the spatial and size distribution of suspended particulate matter on its backscattering properties is of great importance for understanding water body scattering properties and improving inversion accuracy, which is greatly helpful for marine environmental monitoring. Based on the field data of Bohai Sea in June and September 2017, the total suspended particulate matter concentration (SPM), particle size, backscattering coefficient as well as other parameters were obtained. The results showed that the backscattering coefficient (b_bp(λ)) decreased with the increase of wavelength in the visible wave bands. In summer and autumn, the changing trend of b_bp(550) was consistent with that of SPM at most stations; however, the correlation coefficient R² between them was only 0.24. In addition, the relationship between mean particle size (D_A), median particle size (D₅₀) and b_bp(λ) was established in the study respectively. D_A and b_bp(λ) had a linear relationship, and their relationship was better in summer than in autumn by the influence of particle composition, R² was 0.7 in summer and was only 0.3 in autumn. At the same time, it is concluded that the b_bp(λ) increased with the increase of D_A when the water body was dominated by small particles, but while the water body was dominated by large particles, b_bp(λ) decreased with the increase of D_A. D₅₀ and b_bp(λ) showed a different relationship and had a good power exponential relationship, the more small particles in the water, the higher the particle backscattering coefficients value, and the correlation coefficient was 0.66 and 0.5 in summer and autumn, respectively. The influence of particle size distribution on b_bp(λ) was difficult to be determined if without considering the seasonal difference.