Based on the measured scattering and absorption coefficient at fifty points in Taihu lake in winter and summer, the profile distribution of water-leaving radiation contribution and the depth of the same contribution of water-leaving radiation at different point in Taihu lake are simulated by multiple scattering models assurning that the radiation field has no internal light source, no inelastic scattering and the water is uniformly mixed. The results show that, the depth for the sum of water-leaving radiation contribution reaching 99.5% (accumulated downward from the surface) has significant difference in different space on the account of wind wave action and the concentration of phytoplankton in winter and in summer. In summer, the smallest depth is in Meiliang bay and Zhushan bay, followed by the center of the lake and Gonghu bay, in the south-east of Taihu lake the depth is the biggest and the contribution of sediments reflection in east Taihu lake and Xishan hills can not be ignored. In winter, the sediments reflection need to doesn′t be considered since the depth for the sum of water-leaving radiation contribution reaching 99.5% is less than the water depth. In Meiliang Bay, Zhushan Bay, western coast, Gonghu Bay, east Taihu Lake and Xishan Hills the depth is relatively large, but not more than 450 mm. In summer the suspended particulate and chlorophyll are the mainly factors which effected the depth, in winter the mainly factor is suspended particle. The spatial inhomogeneous distribution of the interior water body optical characters determins the spatial difference of the water-leaving radiation contribution which is caused by the upward radiation due to the different depth scattering. Coupling the profile distribution of water-leaving radiation contribution has a great improvement on remote sensing of the quality parameters of water Ⅱ.