Abstract: Simulating experiments were conducted to study the effects of sand and gravel mulches with different sizes on moisture evaporation from soil surface. Sand and gravels with the diameters of 0.5, 2.5, 4.5 cm were used in the experiments and bare surface was taken as contrast. The results indicate that the sand and gravel mulches can efficiently inhibit soil moisture evaporation, especialy at the high level of soil water content. Under the same soil water content and sand and gravel mulches with thickness of 5 cm, inhibitory effects of gravel mulches on the evaporation are negatively correlated with sand and gravel size obviously. Compared with bare surface, the sand and gravel mulches can reduce the soil mositure evaporation and make it at a lower and stable level. The relationship between cumulative soil moisture evaporation and time can be discribed by the linear function under sand and gravel mulching, but logarithm function under bare surface during the successive evaporation of 41 days.