OBJECTIVE： To study the correlation of tacrolimus concentrations among transplant patients’ whole blood， plasma and blood cells， analyze the effects of transplant types and ages on the their correlation， and to provide reference for rational drug use in clinic. METHODS： Totally 20 patients receiving tacrolimus anti-rejection therapy after transplantation and undergoing therapeutic drug monitoring （TDM） were randomly selected. According to the type of transplantation， they were divided into renal transplantation group and lung transplantation group （10 cases for each group）.  According to age， they were divided into three groups： 20-40 years old group， 41-60 years old group and 61-80 years old group （4， 9， 7 cases for each group）. Their residual blood after TDM was collected. Chemiluminescence microparticle immuno assay  （CMIA） was used to detect the concentration of tacrolimus in whole blood. UPLC-MS/MS was used to measure the concentrations of tacrolimus in plasma and blood cells. Pairs plots and Spearman rank correlation analysis were used to analyze the correlation of tacrolimus between whole blood and plasma， between whole blood and blood cells， between plasma and blood cells as well as the effects of transplant types and ages on tacrolimus concentrations among tansplant patient’s whole blood， plasma and blood cells. RESULTS： The correlation of tacrolimus concentrations in whole blood and plasma （r＝0.623，P＜0.01） was slightly stronger than that of whole blood and blood cells （r＝0.591， P＜0.01）； while  the correlation of tacrolimus concentration in plasma and blood cells was relatively weak （r＝0.497，P＜0.05）. Transplant type and age had an effect on the correlation of tacrolimus concentrations among patients’ whole blood， plasma， blood cells. The correlation of tacrolimus concen- tration in whole blood， blood cells and plasma in renal transplantation group was also weak （all r＜0.5）， and was weaker than that in lung transplantation group. The correlation of tacrolimus concentration among whole blood， plasma and blood cells was weak in patients of aged 20-40 years old group （all r＜0.3）， and was weaker than that of patients of aged 41-60 years old group and 61-80 years old group. CONCLUSION： Post-transplantation patients’ tacrolimus concentrations in whole blood， plasma and blood cell have a weak correlation. Rejections and adverse effects should be monitored in these patients， especially those renal transplantation patients or those patients aged 20 to 40.