The interior quality of Shanxi ‘Fuji’ apple including soluble solid content (SSC), sugar content (SC), titrated acidity (TC) and firmness was determined by acousto-optic tunable filter (AOTF) near infrared (NIR) apparatus. The dubitable outlier samples were analyzed by Cook values, Mahalanobis, leverage and studentized residual. In order to avoiding falsely estimating outlier samples, twice-detection diagnosis method was applied to keep more valid samples. The estimated number of outlier samples for SSC, SC, TC and firmness were 11, 11, 11 and 6, respectively. After outlier samples elimination, the correlation coefficient (r) of SSC, SC, TC and firmness models were improved from 0.868, 0.791, 0.443, 0.693 to 0.904, 0.849, 0.501, 0.718, respectively. The RMSEC of SSC, SC, TC and firmness were decreased from 0.882 °Brix, 9.213g/L, 0.805g/L, 0.105MPa to 0.733 °Brix, 7.300g/L, 0.687g/L, 0.097MPa，respectively. Moreover, the presented models of apple quality became more robust and stable.