Abstract: 【Objective】 To address the hot issue of how to use crop growth models to quantitatively analyze the dynamic changes of machine-picked cotton growth under different nitrogen fertilizer operation modes.【Methods】 2-year density and nitrogen fertilizer intercropping experiment was carried out in Aksu cotton area to obtain basic data on aboveground biomass, leaf area index and seed cotton yield, and construct simulation scenarios of nitrogen fertilizer base-tracking ratios and fertility stage allocation ratios, on the basis of which the parameter localization of the RZWQM2 model was completed, and the dynamics of biomass and its characteristics of changes in machine-picked cotton under different nitrogen fertilizer management strategies analyzed and in the end, the effects of these strategies on maximum leaf area index and yield simulation were explored. 【Results】 The model validation results showed that the RZWQM2 model could realize the estimation of the growth dynamics of cotton from seedling to maturity. The average validation accuracy of LAI was 0.43 and 10.71% for RMSE and NRMSE, respectively, and the average RMSE, MRE and NRMSE of aboveground biomass during the validation process were 593.01 kg/hm², 17.6% and 11.01%, respectively, and the average MRE of seed cotton yield was 4.36%, with an average d-value of 0.88, which was in good agreement with the predicted values. The results of scenario simulation showed that compared with the conventional treatment (N₂₇₁), the K value of N₁₆₃ biomass was increased by 1.18%, the maximum growth rate (V_m) of reproductive organs was increased by 1.16%, and the rapid growth period (Δt) was shortened by 0.89%. And N₁₆₃ finally allocated 64.15% of biomass to cotton bolls, which improved the allocation index by 1.38%, and seed cotton yield was significantly and positively correlated with K, V_m, and reproductive organ PI. Maximum leaf area index, seed cotton yield performance with the increase of base tracking ratio first increased and then decreased. In the subsequent period, the increase of nitrogen application showed a trend of first increase and then decreased, the peak appeared in the base tracking ratio of 3∶7, and the transport ratio of N₁₆₃, compared with the conventional treatment, were 1.58% and 5.48% higher, respectively. 【Conclusion】 In a word, the RZWQM2 model can be used as an important prediction tool for nitrogen management decisions. Under the conditions of this study, a reasonable base-tracking ratio and appropriate backward movement of nitrogen fertilizer during the cotton fertility period is an effective nitrogen management strategy, and this study can provide a scientific decision for rational nitrogen application, which promotes accurate and efficient management of nitrogen fertilizer.