Orthogonal signal correction (OSC) and net analyte preprocessing (NAP) were respectively used to pretreat the near infrared (NIR) spectra of apples ranging from 1300 nm to 2100 nm, and the models of sugar content were developed from these two pretreated spectra by the partial least square (OSC/PLS models and NAP/PLS models). Results showed that the optimal number of factors used in OSC/PLS models and NAP/PLS models would reduce as the number of OSC factors and NAP factors increased on by one, even to 1 finally. The best OSC/PLS model with 2 PLS factors was obtained when 10 OSC factors were used in pretreatment; and the best NAP/PLS model with 1 PLS factor was obtained when 11 NAP factors were used in pretreatment. Although the best OSC/PLS model and the best NAP/PLS model didn't improve precision to a great extent, they needed fewer factors and became more parsimonious, compared with the model before NAP pretreatment. In a conclusion, OSC and NAP pretreatment could simplify the prediction model of sugar content.