Abstract: A compound preservative for prolonging the storage period of onion paste Nang was studied. Picking up the total number of colonies and pH as indicators, based on the single factor test of different preservatives. Three preservatives with significant benign changes were chosen for the response surface test with the total number of colonies as the response value. The sole factor effect and analysis of variance showed that the primary and secondary order of the three factors was: External control preservative>sodium dehydrogenate>sodium diacetate. The interaction between sodium diacetate and sodium dehydrogenate and the interaction between sodium diacetate and external control preservative had synergistic effect, and the synergistic effect of the latter was stronger than the former, but there was no synergistic effect between sodium dehydrogenate and external control preservative. The optimum formula of compound preservative was sodium diacetate 1.06 g/kg, external control preservative 1.33 tablets/200 g and sodium dehydrogenate 0.16 g/kg. After storage for 6 days at room temperature (27~30 ℃), the total number of colonies of onion pulp Nang was (2.61±0.02) lg CFU/g, and the storage life could reach 23 days. The results showed that the compound preservative could significantly improve the antibacterial effect of onion paste Nang and it was of great significance to prolong the shelf life of onion paste Nang.