Sediment diffusion theory is widely used in the study of suspended load sediment concentration vertical distribution. The paper introduced diffusion theory that derives sand Rouse formula, Zhang Xiaofeng formula and Zagustin formula.It used coarse and fine sediment to verify respectively the three formulas, and analyzed the results.The results show that under the condition of coarse particle, Zhang Xiaofeng formula has more precision; under the condition of fine particle , there are large difference between the results of three formulas and experiment data,but Rouse and Zagustin formula show higher precision after revising distribution index.