Abstract: Objective To evaluate the effect of closed system drug transfer device (CSTD) on the residual amount of cytotoxic drugs in the pharmacy intravenous admixture services (PIVAS). Methods Using cyclophosphamide as an example drug, WIPE samples and High performance liquid chromatography (HPLC) are used to quantitatively detect the residual of cyclophosphamide in the PIVAS of Fudan University Shanghai Cancer Center. Three batches of samples were taken before and after-cleaning at the end of one working day of dispensing in a conventional formulation method, and also after three weeks of continuous application of CSTD for dispensing. The samples were taken from 19 positions including the working surfaces of three biological safety cabinet, transport cart and export table. The residual amount of cyclophosphamide in the three batches of samples was compared. Results The median value of monitoring points before decontamination was 1.30 (IRQ: 0.24, 2.60) ng/cm², and the median value after decontamination was 0.22 (IRQ: 0.08, 0.53) ng/cm². There were significant differences between before and after decontamination (P<0.001). After implementation in the CSTD, the median value of monitoring points before decontamination was 0.06 (0.02, 0.88) ng/cm², which was significantly lower than that before the regular decontamination (P<0.001), and also lower than the after regular decontamination, but the difference was not significant (P=0.299). Conclusion The application of CSTD can effectively reduce environmental contamination of cytotoxic drug in the process of dispensing and transportation, thus significantly reduce occupational exposure to toxic drugs by relevant medical staff.