Objective To study the bacteriostatic activity and stability of pine bark Oligomeric Proantho Cyanidins. Methods By the K-B disk diffusion method, spoilage bacteria as experiment strains, to study the inhibition effects of the pine bark Oligomeric Proantho Cyanidins and the antimicrobial stability under certain temperature, pH, and UV exposure time. Results Pine bark Oligomeric Proantho Cyanidins had significant inhibitory effect on Gram positive bacteria (Staphylococcus aureus and Bacillus Sukatilis), which had better inhibition effects in the media neutral, but temperature and UV had little influence on the antimicrobial effects. The minimum inhibitory concentration (MIC) of pine bark Oligomeric Proantho Cyanidins against Staphylococcus aureus and Bacillus Sukatilis were 12.5 and 6.25 mg/mL, respective. However, on Gram negative bacteria(Escherichia coli and Pseudomonas aeruginosa) there was no obvious inhibition effects. Conclusion The pine bark Oligomeric Proantho Cyanidins has significant inhibitory effect on Gram positive bacteria, the inhibitory effect is stronger in the range of pH 6-7 , and the temperature and UV had a little effect on its antibacterial action, which means that the antibacterial action of pine bark Oligomeric Proantho Cyanidins had good stability.