Abstract: One strain of endophytic fungus ZPRa-R-1 was obtained for the capacity of promoting production of salidroside in Rhodiola crenulata. To explain the mechanism of salidroside biosynthesis in host plant, eight housekeeping genes were evaluated, and the evaluation method was created for the expression activities of four key enzyme genes PAL (phenylalanine ammonia-lyase), TyDC (tyrosine decarboxylase), TAT (tyrosine transaminase), UDPGT (UDP-glucosyltransferase) referenced double reference genes in biosynthesis pathway of salidroside in R. crenulata. Stabilities of housekeeping genes were confirmed by real-time fluorescent quantitative PCR technology and three softwares including geNorm, NormFinder and BestKeeper, then relative expressions of key enzyme genes were analysized by the 2^-ΔΔCt method. The results showed that the most stable gene was GAPDH, followed by PCS, and the most appropriate reference of internal genes were combination with two genes in R. crenulata inoculated with endophytic fungus ZPRa-R-1. Under symbiosis conditions, regularity changes of key enzyme genes affected by endophytic fungus ZPRa-R-1 were as follows:the relative expression activity of PAL attached to peak value, which was 4.9 times as that of control group when inoculated ten days. The relative expression of TyDC reached the maximum value, which was 2.8 times of that control after inoculating 12 days. The relative expression of UDPGT actually reach 17.1 times than that of control after inoculating 8 days. However, the relative expression of TAT was not affected by this fungus. The changes of four key enzyme genes are positively correlated with the changes of salidroside content in R. crenulata.