GIP, the acronym from gastric inhibitory peptide or glucose-dependent insulinotropic polypeptide, which is a kind of gastrointestinal regulatory peptide composed of 42 amino acids, plays an important role in stimulating insulin releasing in the pancreas,inhibiting gastric acid secretion in the stomach, as well as inducing progenitor cell proliferation in the brain. The application of GIP is promising in clinic. It is difficult and costly to get GIP with chemical extraction method, and it can't be produced cosmically, so it is valuable and significant to produce recombinant GIP by genetics and test its bioactivity. The cDNA sequence coding for human GIP mature peptide and composing of preferred codons of E. coli. was synthesized, and was expressed in prokaryotic expression pET32a(+) system. The recombinant E. coli was fermented in a small scale and the expression condition was optimized. The expressed recombinant human GIP (rhGIP) was purified by affinity method. The bioactivity of the purified rhGIP was tested through its effect on inhibiting gastric acid secretion and decreasing blood glucose concentration in SD rats. The effect on PC12 cell producing NO free radical was assessed through morphology observation and the NO concentration test. A PC12 cell injury model was constructed by adding Aβ_25-35 into the culture medium, different dose of rhGIP was added into this model, and the activity of PC12 was tested by MTT (2-(4,5-dimethylthia-zol-2-yl)-2,5-diphenyltetrazolium bromide) staining. The results suggest that hGIP gene is cloned successfully, the recombinant protein constitutes 35% of the total protein of the cells, some of which was soluble, while the others exist as inclusion body. The relative molecular mass of the recombinant protein is 26 ku as expected. The purified rhGIP showed immunoreactivity. The optimal condition for inducing to expression is with the cell concentration of 0.5 in A₆₀₀ value, the IPTG concentration of 0.5 mmol/L, under 37℃ and induced for 4 h. The cell lysis supernatant was purified with immobilized metal affinity chromatograph. The production of soluble rhGIP is about 1.2 mg/L culture medium, and the purity is 85%. Purified rhGIP significantly inhibited the secretion of gastric acid and raised the pH value comparing with NC group in SD rats (P < 0.05). There was no significant difference between the rhGIP and standard GIP group (P 0.05).After injection of rhGIP for 15 min, the concentration of blood glucose in plasma decreased remarkably comparing with control group in a high blood glucose environment (P < 0.05). In the later 30 min, there was no remarkable difference (P > 0.05). Also, there was no difference between rhGIP and standard GIP group (P > 0.05).In the research to test the effect of rhGIP on cell nutrition and PC12 cell to avoid neural injury and anoxic injury, it was found that the level of NO was significantly decreased (P < 0.01), the survival rate of the PC12 cells was increased, and neurite extending was better. The activity of the high and medium rhGIP concentration group is higher than that of neural injury group and anoxic injury group (P < 0.05), and the activity is increased as dose-dependence. The differences among rhGIP, GIP and NC group is not remarkable (P > 0.05). The results showed that the rhGIP has been successfully expressed and purified and showed obvious immunoactivity. The recombinant product was shown to have a wide spectrum of biological activity, such as inhibiting gastric acid secretion in the rats stomach, decreasing the concentration of blood sugar in plasma, as well as nutrition and protection to neural cells.