In order to apply tachyplesin, a high-perforvaance and broad-spectrum antibacterial peptide to the pharmaceutical industry, the biological stability of tachyplesin varying with the temperature, the pH value and the proteinases such as trypsin, pepsin, elastase and caboxypeptidase B was investigated and was described by the minimal inhibitory concentration （ MIC ）. Moreover, the stability of molecular structure was evaluated by the peak change in high-performance liquid chromatography （HPLC）. The results indicate that （1） at 120℃, when the pH value reaches 11.30, the MIC of tachyplesin against E. Coli K88 ranges from 1.25 to 5.0 mg/L and the residual content of tachyplesin detected by HPLC varies from 65. 46 to 70. 21 μg; （2） tachyplesin is sensitive to trypsin, carboxypeptidase B and elastase, but remains stable with pepsin; and （3） tachyplesin is stable in the solution with the pepsin, trypsin carboxypeptidase B and elastase contents of not more than 5. 33 mmol/（ s· L）, 0. 33 mmol/（ s · L ）, 0. 17 mmol/（ s·L） and 0. 021 mmol/（s · L）, respectively. It is thus concluded that tachyplesin is of high heat resistance, good stability and excellent anti-enzymatic degradability.