Abstract: Fenneropenaeus chinensis is nutritious with high economic value, but is easy to blacken during circulation and storage. Thus, in order to promote the standardized utilization of anti-blackening preservatives for shrimps and optimize their efficacy, we selected sodium metabisulfite and 4-hexylresorcinol (4-HR) as fundational components, both approved for use in the Standard for the Use of Food Additives (GB 2760−2014), and screened natural ingredients with anti-blackening effects, compounding them with sodium metabisulfite and 4-HR. Besides, by using phenoloxidase (PO) activity as a key indiex, we systematically determined the optimal ratio of this composite preservative through an orthogonal test. Then, we assessed its practical efficacy. The results show that the most effective formulation was: 3.0 g·L^–1 ascorbic acid, 5.0 g·L^–1 bamboo leaf antioxidant, 15.0 g·L^–1 sodium metabisulfite and 50.0 mg·L^–1 4-HR. The composite preservative demonstrated a remarkable capacity to mitigate blackening in F. chinensis compared with the control group. Moreover, application of the composite preservative resulted in significantly reduced levels of thiobarbituric acid reactants (TBARS), total volatile basic nitrogen (TVB-N) and total bacterial counts in F. chinensis during refrigeration, all significantly lower than those of the control group. Microbial diversity analysis reveales a pronounced inhibition of the dominant genus Photobacterium during the spoilage process of F. chinensis treated with the composite preservative. In conclusion, this composite preservative not only meets with the GB 2760 standards, but also exhibits exceptional anti-blackening and preservation effects, with good application prospects.