Abstract: It was observed that the outer_layer cells of the pericarp of antisense PG transgenic tomato were 1～5 μm thicker than those of nontransgenic tomato, and clear differences existed in cell structure and cytoplasm and nucleus status between the fruits of the transgenic and nontransgenic tomatoe at different stages of fruit ripening and storage, especially at the end of storage. The fruit of nontransgenic tomato showed a serious collapse of pericarp cell structure, condensat ion of cytoplasm and blurring of nucleus, compared with that of the transgenic tomato. Exogenous ethylene treatment caused similar changes in cell structure of the fruits of transgenic and nontransgenic tomatoes. These results demonstrated that the expression of the antisense PG gene in tomato fruit effectively inhibited the activity of endogenous PG, reduced the effect of ethylene and prolonged the time of fruit storage.