In order to obtain the multispectral image of the non-destructive test sample, a method of obtaining the multispectral image by using the liquid crystal tunable filter (LCTF) is studied. LCTF has the functions of light modulation, deflection and filtering. The cascade of multi-stage Lyot wave plates can be electronically tuned in a wide spectral band. By changing the applied voltage, the dynamic modulation of the filter can be realized to obtain high-precision narrow-band spectral output. Compared with the traditional multi-spectral image obtaine by using the multi-spectral spectrometer, LCTF has the advantages of simple control, low modulation voltage, fast continuous modulation and so on. In this paper, the voltage phase delay characteristics of a group of wave plates are measured by the quarter-wave retarder method, and the appropriate wave plates are selected to form a triple filter to realize the narrow-band filtering of the broadband spectrum. A multispectral imaging system is obtained by this method to realize non-destructive testing for fruit quality.