To use polydopamine(PDA)to carry out multiple components of Salvia miltiorrhiza injection,and to construct a slow-release preparation of Salvia miltiorrhiza injection(SMI)(PDA-SMI).Methods:Establish the analysis method of the three components of protocatechuic aldehyde,rosmarinic acid and salvianolic acid B of Salvia miltiorrhiza injection and determine the content; prepare PDA,load SMI under the condition of pH 2.5 to prepare PDA-SMI; The in vitro release behavior of PDA-SMI was investigated.Results:The concentrations of protocatechuic aldehyde,rosmarinic acid and salvianolic acid B in SMI were 0.344,0.214 and 0.262 mg/mL,respectively; the loading of protocatechuic aldehyde,rosmarinic acid and salvianolic acid B by PDA-SMI The doses were 8.59%,15.90% and 20.57% respectively; the cumulative release rates of protocatechuic aldehyde,rosmarinic acid and salvianolic acid B in PDA-SMI were 84.05%,77.57% and 63.12%,respectively.Conclusion:PDA can load multiple components of SMI and has a good sustained-release effect.