Objective The aim was to search for a better freshness-preserving agent for the preservation of sea prawn.Methods It was compared that effect of 4 freshness-preserving agents (Na_2S_2O_5, FMP natural color-protecting agent, Shiweixian-Xiaxianbao and phytic acid) and 3 ways of applying the agents (dipping, splashing and powder scaffering).Results The experimental results indicated: Na_2S_2O_5 showed better preserving effect within seven days. But excess residue of SO_2 will appear if operated improperly. FMP natural color-protecting agent and Shiweixian-Xiaxianbao both showed better preserving effect. The preserving effect of phytic acid was not so good. Comparing dipping and splashing in the same concentration of preserving agent, dipping showed better preserving effect.Conclusion Economically, dipping the prawn three minutes in 1.5% Na_2S_2O_5 solution can effectively preserve its freshness. Taking into account the consumer's health, dipping in 2% FMP natural color-protecting agent or Shiweixian-Xiaxianbao for three minutes is a better practice. The preserving effect will be better when the time of preservation is less than within seven days.