Abstract: In order to find out the relationship between leaf area index(LAI)and characteristics of canopy reflection spectrum of flue-cured tobacco,the spectral reflectance of tobacco canopy against different LAI was measured and the quantitative relationship between them was analyzed.The results showed that LAI negatively related to the reflectance of visible light band in reflection spectrum,while significantly positively related to that of near infrared band.The correlation coefficient of reflectance at 1100 nm to LAI was the highest in the range of visible light band(r=0.816).Almost all the correlation coefficients of vegetation index composed of the two frequency bands to LAI reached significant level,of which the normalized difference vegetation index(1100,600)against LAI was found to be the biggest(r=0.895).The model formed with NDVI(1100,600)was used to predict LAI in this experiment,it gave pretty good results.