Abstract: In the various of mine exploitation sites,there are many loose debris and earth from strata. And it is a usual existing appearance that people throw the spoil,debris and earth to near river bed or in vally of gully. According to analyzing and calculating,this accumulation will lead to serious soil erosion,and usually forming debris flow,which can give rise to harm and disaster to mine development,surounding ecologic environment and people's life of lower reches On the basis of field investigation and with the maths,the erosion process of loose spoil and earth from mine exploitation on slope of river or in the vally has been analyzed,and a methed used to estimating total eroded quantity of those loose materials for environmental evaluating.