Algorithm of terrain factors of GIS pixel is the key technique in monitoring soil loss by remote sensing. The principle, the applied process and the applied results of this algolithm are introduced and its applied accuracy is discuced in this article. Although the algorithm of terrain factors of GIS pixel is more complicated, and its calculation is more complicated than that of contour terrain factors, it is more dependable, automatic and of a higher accuracy than the latter algorithm. Neglecting the slope-length factor of pixel or regarding it as the same constant value due to similar slope lengths of pixels would lead to bad mistakes in the soil loss monitortng.