A portable solar-induced chlorophyll fluorescence monitor based on this principle was developed and tested. The instrument uses sunlight as its light source. There are two sets of photoelectrical detectors with the center wavelength at 760nm and 771nm respectively and the bandwidth of each detector is 1?nm. Both sets of detectors are composed of an upper detector which are used for detecting incidence sunlight and a bottom detector which are used for detecting reflected light from the canopy of crop. The detector is the core of the monitor to measure the spectrums at special bands. The microprocessor calculates solar-induced fluorescence value based on the A/D values obtained from detectors. And the value can be displayed on the LCD, stored in the flash memory and uploaded to PC through the PC's serial interface. The prototype was tested in the crop field at different view directions and the results demonstrated that the instrument could measure the solar-induced chlorophyll value accurately with the correlation coefficients higher than 0.9 compared with the values obtained from analytical spectral devices FieldSpec Pro NIR spectrometer.