¹³⁷Cs method was used to study soil erosion and sediment transportation in the farmlands on Mao (round loess mound) and slopes in North Shaanxi in this paper. A quantitative analysis was made of the erosion properties on Mao and slopes. The results indicated that erosion on Mao and slopes appeared to fluctuate very strongly, weakly, and very strongly again, and then weakly from the ups to the downs. Also, erosion equation for non-agricultural lands and agricultural lands has been used to calculate the modulus of erosion in non-agricultural lands on the Mao top since 1963, being 1 068 t/(km²·a), while the modulus of erosion in agricultural lands is 4059 t/(km²·a), Also, a comparative analysis was made of actual determined modulus of erosion of sloping farmlands in the runoff experimental fields on Liang (elongated loess mound) , Mao and slopes.