AbstractPhenolic acids are the main bioactive compounds inSalvia miltiorrhiza, which can be increased by salicylic acid (SA) elicitation. However, the specific molecular mechanism remains unclear. The nonexpresser of PR genes 1 (NPR1) and its family members are essential components of the SA signaling pathway. Here, we report an NPR protein, SmNPR4, that showed strong expression in hairy root after SA treatment, acting as a negative moderator of SA-induced phenolic acid biosynthesis inS. miltiorrhiza(S. miltiorrhiza). Moreover, a basic leucine zipper family transcription factor SmTGA5 was identified and was found to interact with SmNPR4. SmTGA5 activates the expression of phenolic acid biosynthesis geneSmTAT1through binding to theas-1element. Finally, a series of biochemical assays and dual gene overexpression analysis demonstrated that the SmNPR4 significantly inhibited the function of SmTGA5, and SA can alleviate the inhibitory effect of SmNPR4 on SmTGA5. Overall, our results reveal the molecular mechanism of salicylic acid regulating phenolic acid biosynthesis inS. miltiorrhizaand provide new insights for SA signaling to regulate secondary metabolic biosynthesis.