Background Tanjin is an herbal medicine made from the root of salvia miltiorrhiza. It is predominantly given to arteriosclerotic patients as a supplement to ameliorate the clinical symptoms of cardiovascular diseases. In China, tanjin is used frequently in combination treatment for hypercholesterolemia. Thus, there is a high probability of combination of tanjin and statins in these arteriosclerotic patients. This study investigated the interaction between tanjin and rosuvastatin. Methods We performed a randomized single-blind, two-period crossover clinical trial on six healthy male volunteers. Volunteers were administered rosuvastatin with placebo or a tanjin-containing drug randomly. The blood samples were collected before drug administration, and at 0.5, 1, 1.5, 2, 4, 8, and 12 hours after administration. Lymphocytes were isolated from blood samples before and 12 hours after drug administration to measure mRNA. As an animal experiment, an in situ intestinal injection with portal vein sampling model was used to examine the interaction between tanjin and rosuvastatin during the absorption phase. Rosuvastatin or rosuvastatin combined with tanjin solution was injected into the intestine. After injection, blood from the portal vein was collected and the concentration of rosuvastatin was measured by LC/MS/MS analysis. A portion of the intestine and liver from the rats was collected and stored at-80°C for mRNA measurement. Results In the clinical trial, co-administration of tanjin decreased the maximum plasma concentration (C max) of rosuvastatin by 26.85% compared with rosuvastatin alone, and also decreased the area under the plasma