To probe into the primary and secondary relation of factors influencing runoff coefficient,based on the grey system theory,a grey correlation analysis on factors which is herb layer coverage,litter layer thickness,shrub layer coverage and canopy density surface runoff was made,using the data measured in different vegetation types of Jinyun mountain,Chongqing.The results indicate that the effects on surface runoff coefficient by the parameters of vegetation status is herb layer coverage(0.772 0)> litter layer thickness(0.744 5) > shrub layer coverage(0.666 1)> canopy density(0.614 2).The mixed wood and broadleaf forest has better effect on surface runoff coefficient in different vegetation types,the grey correlation degree is 0.634 56,0.618 5 in turn.The bamboo forest has the smallest effect on surface runoff coefficient,the grey correlation degree is 0.500 0.It is prove the mixed wood and broadleaf forest has better hydrological and ecological function.