The aim of the study is to compare the effect of boiling and high pressure steaming (HPS) on the degradation, inhibitory activity reduction and gastric digestibility of soybean trypsin inhibitor (STI). Thermal stability analysis showed that HPS treatment was effective in eliminating the inhibitory activity of STI than boiling. SDS-PAGE and Western blot analysis indicated that boiling has less impact on the gastric digestibility of STI than HPS. More importantly, boiling-pretreated STI revealed high inhibitory activity against trypsin even after digestion by pepsin in simulated gastric fluid (SGF), while HPS treatment was more effective. SDS-PAGE analysis further verified that after boiling, STI still revealed strong binding ability to trypsin, while STI could be completely degraded by trypsin after HPS treatment for 30 min.