By using quantitative geomorphical method and taking the Wuding River basin as an example,this paper puts forward the conceptof exposure surface of landform,which represents the possible erosive area in a region,and deals with the geomorphic conditions effecting loess erosion.The relations between each pair of morphological parameters are as follows: D=12.89H^0.69 r=0.77 D=0.374A^0.778 r=0.94 D=-4.061g^L-2.13 r=-0.9 H=0.014A^0.85 r=0.92 S_p=0.9+0.85L r=0.83 S_p=0.559A^0.66 r=0.94 where D is gully-valley density (km/km²),H is relative height (km),L is length of slope (km),A is average angle of slope and S_p is potential expos-ure surface of landform (km²/km²).Most of them are significant at 0.01 level.The author thinks that the models can be used to predict the intensi-ty of loess erosion. M=3046.45+73.23H r=0.83 M=27.54S_p^1.27 r=0.98 where M is the soil erosion modulus (T/km²·yr).