Laser in situ scattering and transmissometry(LISST) significantly improves our ability to assess particle size distribu-tion(PSD) in seawater, while wide-ranging measurements of the organic-inorganic compositions of suspended particulate matters(SPM) are still difficult by using traditional methods such as microscopy. In this study, PSD properties and SPM compositions around the Bohai Strait(China) were investigated based on the measurements by LISST in combination with hydro-biological parameters collected from a field survey in summer 2014. Four typical PSD shapes were found in the region, namely right-peak, left-peak, dou-ble-peak and negative-skew shapes. The double-peak and negative-skew shapes may interconvert into each other along with strong hydrodynamic variation. In the upper layer of the Bohai Sea, organic particles were in the majority, with inorganic particles rarely observed. In the bottom layer, SPM were the mixture of organic and inorganic matters. LISST provided valuable baseline information on size-resolved organic-inorganic compositions of SPM: the size of organic particles mainly ranged from 4 to 20 μm and 40 to 100 μm, while most SPM ranging from 20 to 40 μm were composed of inorganic sediment. Laser in situ scattering and transmissometry (LISST) significantly improves our ability to assess particle size distribu- tion (PSD) in seawater, while wide-ranging measurements of the organic-inorganic compositions of suspended particulate matter (SPM) are still difficult by using traditional Methods such as microscopy. In this study, PSD properties and SPM compositions around the Bohai Strait (China) were investigated based on the measurements by LISST in combination with hydro-biological parameters collected from a field survey in summer 2014. Four typical PSD shapes were found in the region, ie right-peak, left-peak, dou-ble-peak and negative-skew shapes. The double-peak and negative-skew shapes. the Bohai Sea, organic particles were in the majority, with inorganic particles rarely observed. In the bottom layer, SPM were the mixture of organic and inorganic matters. le baseline information on size-resolved organic-inorganic compositions of SPM: the size of organic particles mainly ranged from 4 to 20 μm and 40 to 100 μm, while most SPM ranging from 20 to 40 μm were composed of inorganic sediment.