In order to explore a non-destructive method in identifying kiwifruit ripeness, a near infrared diffused spectroscopy technology was used to determine firmness of Huayou kiwifruits during cool storage. Partial least squares (PLS) regression was carried out to analyze the spectroscopy. Four different spectral pretreatment methods were used to compare calibration results for firmness. The result showed that the best calibration models, in the whole wavelength range, could be obtained by the first derivative spectrum with the correlation coefficient of calibration of 0.963 and the correlation coefficient of prediction of 0.852. 