Abstract: Based on the observed rainfall and runoff data in 11 rainstorm events during the flood season from 1997 to 2007 at three different spatial scales (plot: 1600m2, field: 6 hm2 and small catchment: 1.36km2) in Huaibei Plain, China, the scale effects of storm-runoff processes in agricultural areas of Huaibei Plain were analyzed. The differences in storm-runoff processes and their main influences at different scales in agricultural area were evaluated. Results showed the storm-runoff process at the small plot was obviously different from that in the other two catchments, and the runoff depth is smaller and flood peak modulus is larger in the small plot than in the field and two catchments during same rainstorm event. At the plot scale, there is no lateral groundwater discharge process, which may be the main reason for the different storm-runoff processes. The runoff processes in the 6 hm2 field and 1.36 km2 catchments were similar, but the runoff depth and flood peak modulus at the catchment 1.36 km2 is smaller than that at the middle scale. This research indicated that storage capacity in the large scale may be the main reason for the smaller runoff depth and flood peak modulus.