By contrast natural light fruit,the fruit of Ziziphus jujuba Mill.cv.lingwuchangzao were treated with shielding light at full flowering stage.The fruit growth index,chlorophyll content,enzyme activities of the sucrose metabolism and sugar content were measured to study the effects of photosynthesis on accumulation of fruit sugar and the content of polysaccharide and total sugar.The result showed that:(1)The weight and fruit volume of single fruit and content of chlorophyll reduced after shielding light treatment.(2)The activities of fruit invertase,sucrose phosphate synthase and the decomposition enzyme of sucrose synthase increased but the activities of the synthetic enzyme of sucrose synthase reduced with the different extent of shielding light treatment.(3)Shielding light treatment mainly affected sugar content in stages of color changing and ripe stage,but little effect on initial period of fruit development.In conclusion,the formation of polysaccharide in fruit had the certain relations to normal illumination,but the accumulation of total sugar in fruit had close relations to illumination.To sum up,shielding light treatment affected sugar metabolism and accumulation by influence enzyme activities of the sucrose metabolism in developmental fruit.