Based on the data of artificial rain obtained from 42 experimental plots on the different eroded soils including red earths derved from quaternary red clay and granite and puple soils in Xingguo County of Jiangxi Province,the equations,W=aT^b,V =aT^b and M=(a+b/T)^-1, were established by curve-fitting method to give expression to the relationship between raining duration and runoff coefficient,infiltration time and its rate,and infiltration time and its capacity.These equations are of practical significance for revealing the characteristics of runoff and permeability,estimating the amount of runoff and loss of soil by erosion and evalusting the beneficial effect of soil conservation.