Abstract: 【Objective】 Fe element is an important index to evaluate plant growth, and monitoring nutritional status is one of the main contents in the process of fruit tree cultivation and management. This project aims to realize monitoring of foliar Fe content in Juglans regia L.in vivo by analyzing the relationship between foliar Fe content in Juglans regia L. and foliar spectra in the hope of providing theoretical basis and technical support for rapid diagnosis of Fe content. 【Method】 Eight Juglans regia L. production garden were selected in Aksu Hongqipo area for random sampling, the spectral reflectance and Fe content of the foliar were measured. The method of stepwise linear regression and principal component regression was used to construct the estimation model of Fe content. Random grouping method was used to select test samples and evaluate the accuracy. 【Result】 The correlation between the content of Fe in Juglans regia L. foliar and spectra transformed by differential, logarithm and so on was significantly higher than that of the original spectrum. In these data conversions, the highest accuracy of the model was principal component regression model, which was based on the logarithmic second-order spectra of 725-730 nm, 1,140 nm, 1,141 nm, 1,443 nm, 1,444 nm and 1,445 nm. So the optimal model for monitoring foliar Fe element of Juglans regia L. was y=558.648+113.024 PC₁³-31.514 PC₁² +71.519 PC₁, R² was 0.870, RMSE was 0.304, RPO was 2.39. 【Conclusion】 Spectral technique has a certain application potential in estimating the Fe content of Juglans regia L. in Hongqipo area of Aksu.