Manilensis is one of the major pests in China. A method for recognizing different ages of manilensis was presented based on Kmeans clustering and principal component analysis (PCA) with selected feature wavelength. The hyperspectral images in the range of 400~1000nm of manilensis back at differnet ages among adult, 5age, 4age and 3age were collected and the average spectral information of target region on manilensis back with the size of 15 pixel×15 pixel was extracted. A wavelength secleting method with combined PCA algorithm and Kmeans clustering (K-PCA) was proposed. The model for identifying manilensis ages was built by using Fisher algorithm and then compared with K-PCA algorithm and successive projections algorithm (SPA). The experiment results showed that the K-PCA algorithm needed fewer wavelengths but with the higher accuracy of 98.25%. The final feature wavelengths of K-PCA algorithm were 468nm, 555nm, 635nm, 710nm, 729nm, 750nm, 786nm and 899nm. The proposed method provides a certain technology support for manilensis monitoring and precention.