Abstract: Due to the mixed pixels containing both crops and forest vegetation,there are limitations if the annual mean Normal Difference Vegetation Index(NDVI(I_NDVI,m)) is used as an index reflecting forest coverage.In the Loess plateau region,the seasonal variation of forest cover is quite different from that of crops.On this basis,the NDVI-based index of forest cover may be established by considering some combination of monthly NDVI or weighted average of monthly NDVI with some proper weight coefficients.It has been found that the determinant coefficients of annual forest coverage C_f) with June NDVI and October NDVI are the highest among the 12 months.Hence,the averaged NDVI of June and October(I_NDVI,6+10) were used to reflect annual forest coverage.The determinant coefficient between C_f and I_NDVI,6+10 is 0.538 4,which is 21.48% higher than that between C_f and I_NDVI,m,0.443 2.The determinant coefficient between weighted average of monthly NDVI(I_NDVI,w) and Cf is 0.514 4,16.07% higher than that between Cf and I_NDVI,m.Thus,I_NDVI,w and I_NDVI,6+10 should be used as NDVI-based forest coverage indices in the Loess Plateau region.