Abstract: Surface waxes of Citrus sinensis Osbeck‘Newhall’，C. reticulata Blanco‘Yangxiao 2-6’，C. grandis Osbeck‘Hongxin Miyou’，C. unishiu Marc.‘Miyagawa Wase’and C. limon Burm. F.‘Eureka’mature fruits were studied by crystal morphology and chemical composition levels in this report using scanning electron microscope（SEM）and gas chromatography-mass spectrometry（GC–MC）analysis. The results showed that the surfaces of citrus mature fruits were covered by a amorphous wax layer，on which a lot of irregular platelet wax crystals with different sizes scattered. The waxes of citrus fruit surfaces were mostly composed of fatty acids，alkanes，aldehydes，primary alcohols，triterpenoids and small-molecular metabolites. Among the five citrus cultivars，‘Newhall’navel orange possessed the largest and most wax crystals. Moreover，the total wax loads and the amounts of all wax fractions except for aldehydes on‘Newhall’fruit surface were much higher than other four species. The hexamethoxy flavone with function of health protection was first isolated from the wax layer of‘Newhall’fruit peels in this study.

Key words: citrus, wax crystal, wax composition