Abstract: Based on the diffusion equations of suspended sediment concentration (SSC), we analyzed the inherent irrationality of the free surface condition in some main solutions for the equilibrium profile with different diffusion coefficient expressions, and reconstructed a 1/2 power-law diffusivity expression by geometric mean method according to the distribution characteristics of constant and linear diffusivity profiles, then a new exponent profile was derived for SSC under equilibrium condition in this paper. Through the comparison between the new diffusivity distribution as well as its corresponding SSC profile and a lot of measured data from abundant literatures, together with the study results by van Rijn and Zhang, it is shown that this new exponent profile not only has higher precision in computing SSC, but also is characterized by simple expression, limited bed layer SSC and direct integral which are the distinguished features superior to Rouse equation, van Rijn equation and Zhang equation. Therefore, it is a simple and robust profile for the equilibrium SSC with more superiority in theoretical research and practical applications of hydrology, sedimentology and water resources.