Abstract: In order to solve the problem that output value of existing reflective instrument is easily affected by detection distance，and detection area of instrument is different at different wavelengths，resulting in deviation of detection value，output parameters of existing instruments were optimized and a design scheme for multi-wavelength detection optical path was proposed，based on this，a reflective leaf chlorophyll content detector was developed.Test results showed that maximum fluctuation rate of output voltage of instrument under different lighting conditions was 0.95%，and maximum fluctuation rate of output parameters of instrument under different detection distances was 1.13%.RMSE of the best detection model was 0.105 6 mg/g.It showed that the instrument could adapt to changes in ambient light and detection distance，and detection effect was better，which could provide support for differential analysis of field crops.