OBJECTIVE： To compare the composition changes of Aurantii fructus before and after fermentation processing and optimize its fermentation processing technology. METHODS： UPLC was conducted to compare the raw and fermentation processed products of same batch of Aurantii fructus， and ensure the chromatographic peaks after fermentation processing. Using peak areas of 4 chromatographic peaks and mildew characteristics of samples as index， fermentation temperature， humidity and time as factor， L9（34） orthogonal test was designed to optimize the fermentation processing technology， and verified it. RESULTS： After fermentation processing， Aurantii fructus obviously showed 2 new monosaccharide glycosides components； the optimized fermentation technology was as follows as fermentation temperature of 30 ℃， humidity of 70％ and time of 7 d； verification test results showed RSD of each indicator of decoction pieces prepared by optimized fermentation technology in 3 tests were lower than 2.0％ （n＝3）. CONCLUSIONS： Fermentation processing may lead obvious chemical composition changes in Aurantii fructus； the optimized fermentation processing technology can increase the contents of characteristic peaks.