In order to investigate the dynamic relationship of cotton between leaf area index (LAI) and accumulated total production of thermal effectiveness and photosynthetically active radiation (TEP), plot experiments were conducted with Shiza2 cultivar and Xinluzao43 cultivar and four nitrogen levels were imposed. The dynamic changes of LAI and TEP of the whole growth period in four nitrogen levels were quantificationally analyzed according to normalization process, and relative LAI (RLAI) and relative TEP (RTEP) were dynamically simulated using the Curve Expert. The results indicated that eight analog models showed a better fitting effect and the rational function model which had strong biological significance and a high determination coefficient (R2=0.895) can be more accurate to describe the cotton LAI dynamic correlation than others. The model was checked out with five nitrogen levels from field tests and three different ecological points separated with the high-yield field trials, the verification results showed that the confidence α were 0.169, 0.077, 0.171; determination coefficient R2 were 0.948, 0.964, 0.971; consistency coefficient CC were 0.987, 0.991, 0.989; relative error RE were 6.493%, 4.371%, 7.540%; root mean square error RMSE were 0.188, 0.143 and 0.227m2/m2. The results indicated that the RLAI dynamic model based RTEP description can accurately reflect the dynamic changes in the cotton groups. Further analysis of the effect of regulation and control of cotton groups LAI characteristics parameters of different nitrogen levels showed that the nitrogen usage amount affected the whole groups LAI dynamic regulation, especially the mean LAI; maximum LAI and ratio of the two characteristic parameters. It could be important indicators of improving the cotton leaf blade photosynthetic characteristics and the production.