The variation regularity of winter-wheat leaf area index is studied by use of the SUNSCAN plant canopy analyer to simulate growth and development of winter wheat in the field. According to the modifi- canon of Logistic curve, the semi-empirical formula for estimating leaf area index of winter- wheat is founded to fit the winter- wheat leaf area index from retuming green stage to mature stage. The correlation coefficient is 0. 954 2 between simulated value aril measured value, which is up to positive level(p< 0.O5).The results show that the method mentioned above can well reflect the dynamic change of crop leaf area index.