Abstract: Based on the different incidence of pitting fruit，two navel orange cultivars ‘Cara cara’ navel orange（Citrus sinensis Osbeck‘Cara Cara’）and ‘Newhall’ navel orange（Citrus sinensis Osbeck ‘Newhall’）were used to research on cell wall composition，related enzymes in cell wall metabolism of peel and pitting fruit rate with the KH2PO4 foliar application during ripening. The results showed that the difference existed in the peel thickness，hardness and homogeneity between‘Cara Cara’and‘Newhall’navel orange with the KH2PO4 spraying，the pitting fruit rate of‘Cara Cara’navel orange was significantly decreased. There was a few effects on cell-wall metalbolism and pericarp character in‘Newhall’than‘Cara Cara’navel orange，and there have no significant difference in pitting fruit rate of‘Newhall’between KH2PO4 foliar application and control. The decreasing of polygalacturonase（PG），cellulose（CX），xylanase（Xyn），and peroxidase（POD）activities maybe low the decomposition of protopectin，hemicellulose and cellulose，increase peel hardness and thickness，low pitting fruit incidence.

Key words: navel orange, pitting fruit rate, KH₂PO₄, peel, cell wal metalbolism