The effects of eight natural compounds on quality and shelf life of Pacific white shrimps was investigated. Cinnamaldehyde exhibited both antimicrobial activity and inhibitory ability against polyphenol oxidase (PPO) activity to maintain the quality of the Pacific white shrimp during storage. The kinetic analysis showed that cinnamaldehyde was a noncompetitive inhibitor for PPO of the Pacific white shrimp. The combined preservative was optimized using orthogonal experiment and then the optimal combination was as follows: 0.10% cinnamaldehyde, 0.05% phytic acid and 0.50% sodium alginate. The aerobic plate counts (APC), total volatile bases nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS) assay and sensory analyses were used to investigate the change in the quality of the Pacific white shrimps after applications of different treatments. Based on these studies, shrimps treated with the combined preservative exhibited the lowest APC, TVB-N, and TBARS value among the all treatments by the end of storage. The combined preservative could improve the sensory properties and prolong the shelf life of the Pacific white shrimps to 8～10 days. 