Based on the potted sweet orange ‘An liu(Citrus Sinensis Osbeck cv. Anliu)’, we did some researches of ultrastructural changes in the mesocarp cell wall. Cell wall composition, and related enzymes in cell wall metabolism were done during ripening phase in under water stress condition. Results showed that the activities of polygalacturonase(PG), cellulose(CX) and pectinesterase(PME) were more increased, water stress was more severe in potted plant, and the changes of polyphenoloxidase(PPO) activities was on the contrary. The weights of ionically associated pectin, covalently bound pectin, hemicellulose and cellulose about the composition cell wall was induced with more severe water stress. In addition, the decomposion of ultrastructure in the mesocarp cell wall was accelerated by the more severe water stress.