In order to realize precision management of wheat crop, a spectral analyzer was developed to diagnose crop canopy nutrition, and the performance experiment was conducted in a wheat field. The system consisted of optical system, signal acquisition driver module and controller. The optical sensor could collect spectral reflectance between 300 nm and 1 100 nm. The signal acquisition driver module was used to provide a stable voltage and A/D conversion. A spectral acquisition and control software was developed to receive, display, process and save the collected data. Calibration experiments and field experiments were carried out in wheat experimental field. The correlation between the result measured by the spectral analyzer and the result of ASD FieldSpec HandHeld 2 were analyzed. The results indicated that high correlation existed between the reflectance datasets detected by the two equipments. The minimum coefficient of correlation was 0.991 8. The correlation between the winter wheat chlorophyll content and reflectance measured by instrument was analyzed. Selecting the higher correlation band at 550~900 nm, the principal component analysis was applied to establish chlorophyll forecasting model. The determination coefficient R 2 of the calibration model was 0.575 and the R 2 of the validation model was 0.595. Results show that the developed instrument can effectively detect and evaluate chlorophyll content of wheat canopy, and provide theoretical and technical support for the precision cultivation of wheat.