Abstract: This paper deals with the effect of TDS regulator on the photosynthetic rate, accumulation and product transport in the adult leaves on fruiting branch during the young fruit developmental period of Chinese chestnut and its mechanism. The results indicated that (1)the photosynthetic rate in the leaf treated with TDS regulator(1% and 0.5%)were 4.3 and 2.8 times greater than that in the untreated leaf;(2) the accumulated amount of total soluble sugar and sucrose during the day in the treated leaf(23.9% and 25.9%) were higher than those in the untreated leaf(6.8% and 15.1%);(3)the decreased amount of total soluble sugar,sucrose and starch during the night were obviously more in the treated leaf than those in the untreated leaf. The former were 15.8%,11.7% and 1.7%,while the latter were 10%,3.2% and 0.9% respectively.