Abstract: Salicylic acid (SA) induced nitric oxide (NO) generation, Phenylalanine ammonia-lyase (PAL) activation, and salvianolic acid B (Sal B) biosynthesis. To determine the role of NO in SA-induced Sal B biosynthesis, the effects of NO donor sodium nitroprusside (SNP), NO synthase inhibitor L-NNA(N^ω-nitro-L-arginine), NO scavenger carboxy-2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPITO), and PAL inhibitor L-AOPP (L-2-aminooxygen-3-phenyl acrylic acid) on SA-induced NO generation, PAL activation, and Sal B accumulation were studied individually. Pretreatment of the cells with SNP increased SA-induced NO generation, PAL activation and Sal B accumulation, which suggested that NO activated PAL and was involved in SA-induced Sal B biosynthesis. L-AOPP suppressed PAL activity and Sal B accumulation, but did not affect SA-induced NO generation, indicating that NO acted as an upstream signal of PAL. Results indicated that there was a causal relationship between SA-induced NO generation, PAL activation, and Sal B biosynthesis in Salvia miltiorrhiza suspension cell culture. Via activation of PAL, NO mediated the SA-induced Sal B biosynthesis.