In order to search an appropriate pretreatment method to nondestructive measure vitamin C content of umbilical orange, the effect of 11 pretreatment methods to the model based on PLS has been compared. The results showed that the best effect was wavelet do-noised. Its R was 0.9574, its RMSECV was 3.90, its best wave band was 7501.7～5449.8 cm-1, and its principal element was 8. The wavelet do-noised was an efficient method to nondestructive measure vitamin C content of umbilical orange with near-infrared spectroscopy.