Variability of particulate scattering properties and its possible influencing factors are studied using the in-situ inherent optical properties (IOPs) data obtained during april 2012 in the outside estuary of the Yangtze River. Twelve stations are monitored, and the result shows that the average of particulate backscattering coefficients and backscatter ratios at 488 nm at the surface, 5, 10, 20, 30 m depth are 0.0617, 0.0683, 0.0642, 0.0606, 0.1294 m-1 and 1.77%, 1.92%, 1.94%, 1.98%, 2.15%, respectively. The average of particle refractive index at the five layers is 1.14. Except one or two stations, it varies between 1.1 and 1.2. These show the domination of the inorganic mineral particles in this area, although the absorption peak around 676 nm implies a significant concentration of pigment particles in the water. In conclusion, subject to the abundant input of fresh water from the Yangtze River and the re-suspension of bottom particles, particulate scattering and backscattering dominate the IOPs and their variabilities. Also, non-organic mineral particles are the dominant constituents in seawater. Moreover, the variation of particulate scattering shows strong correlation with the depth.