HtrA1, as serine protease lower expressed in various human solid tumors, can down-regulate cell growth and proliferation. In this study, we focus on whether overexpressed HtrA1 can inhibit the growth of gastric cancer in vitro. This study found the HtrA1 is lower expressed in gastric cancer tissue than in normal gastric tissue. When HtrA1 is highly expressing with recombinant plasmid in gastric cancer cell lines SGC-7901 and AGS, it weakened cell proliferation, invasion, and migration in vitro. These data suggested that HtrA1 as an inhibitor in gastric cancer cells resulted in anti-proliferation, reduced invasion, decreased migration, and suppressed growth and may be an effective molecular targets on gastric cancer treatment.