N nutrition is one of the most important limitation factors for crop growth and yield. Precise and timely monitoring and detection of crop N nutrient conditions is necessary for improving the efficiency of N nutrition using and crop management, reducing environmental pollution caused by over nitrogen fertilizer application. In this paper the canopy reflectance spectra during the whole growth period on tobacco field plots treated with different nitrogen levels were periodically and continually measured. LAI of tobacco of several important growth periods was meanwhile measured. The results showed that tobacco canopy spectral reflectance of different growing periods changed regularly with the increase of nitrogen fertilizer application. The canopy spectral reflectance increased in 7l0~1000 nm, while decreased in 460~680 nm. There was high correlations between NDVI and LAI. The research supply theoretical foundation for tobacco N management.