Abstract: Objective: To explore effects of retinoic acid on gastric cancer cells' differentiation and relevant enzmye activity. Methods: Treated with 10-6 mol/L all-trans retinoic acid(ATRA), gastric cancer cells, BGC-823 and MKN-45, were measured by flow cytometry for cell cycle distribution, by microplate reader for enzyme activity, by 3H-TdR incorporation method for DNA synthetic speed and by MTT method for cell growth rate. Results: After treated with ATRA, BGC-823 was lead to stay in G0/G1 phase, while LDH, ALP and β-G activity was suppressed, the inhibition rates were 22.40 %, 32.94 % and 41.35 %, respectively. DNA synthetic speed was decreased by 41.43 % and growth inhibition rate was 61.03 %. Nevertheless, MKN-45 can't be changed as BGC-823. Conclusion: BGC-823, but not MKN-45, can be induced differentiation and cell growth can be suppressed by ATRA.