Objective: To investigate the methylation pattern of Salvia miltiorrhiza copalyl diphosphate synthase 1 (SmCPS1) promoter in different tissues of S. miltiorrhiza and its correlation with SmCPS1 tissue-differential expression pattern. Method: Bisulfite conversion method was used to detect the methylation rate of SmCPS1 promoter in -1 021 bp (translation start site +1). The expression of SmCPS1 was determined by Real-time quantitative polymerase chain reaction method(Real-time PCR). Result: Methylation sites were mainly distributed in the promoter region between -750 bp to-500 bp

rarely in region below -450 bp. Among the 300 examined sites

72 sites (about 24%) showed a tissue-differential manner. 18 transcription binding regions were found to have methylated sites

and 10 of these regions showed differential methylated sites (DMS).A total of 21 DMS were found to be significantly correlated with SmCPS1(P<0.01);7 DMS

which were in negative correlation with SmCPS1

were found to be mainly distributed in the promoter region between -632 bp to -450 bp;the other 14 DMS

which were in positive correlation with SmCPS1

were distributed in the region beyond -632 bp and below -450 bp. Conclusion: Promoter methylation difference may be the cause of tissue-differential expression pattern of SmCPS1 in S. miltiorrhiza.