Objective: To observe the effect of imbalanced BCAA on metabolism of gastric cancer cell line 800-7901 in Vitro. Methods: L-Valine(L-Val) of MEM culture medium Were restricted to serial levels of 1/2, 1/4, 1/8 or 1/16 concentration of normal With increased L-Leucine(L-Leu) concentration to 1 fold, 2 folds cc 4 folds respectively. Gastric poor differentiated cancer cell line 800-7901 and fetal liver cell were cultured in these culture media. Morphologic character of two cell lines were observed everyday. Total protein mounts were recorded on the 3nd day and 5th day of incubation. Consuming volume of L-Val , L-Les and glucose of 800-7901 were detected respectively. Results :Restricted L-Val to less than 1/8 concentration retard 300-7901 cell's growth, reduced protein volume of SGC-7901. 300-7901 cell required more glucose when L-Val supply was subtracted. At same restricted level of L-Val, increasing L-Val to 4 times increased their glucose utilization. Few effect en fetal liver cell growth was found Con-elusion: Increasing L-Leu and restricting L-Val supply can inhibit growth of cancer cell. Gastric cancer uptake high mount of L-Val for both protein synthesis end energy supply through gluconeogenesis.