Provided is a chemotherapy drug mixing device. The device comprises an annular connecting seat, an upper thrusting needle, a lower thrusting needle and a flow valve, a through hole is formed in the middle of the connecting seat from top to bottom, and the upper thrusting needle and lower thrusting needle are respectively arranged at the upper end and lower end of the through hole located in the middle of the annular connecting seat; a cylindrical groove is transversely arranged in the middle of the annular connecting seat, the flow valve comprises a spring, a piston, a push rod, an installation cover and a handle, and a through hole is formed in the middle of the piston from top to bottom; the spring is placed in the left end of the cylindrical groove, the left portion of the push rod is arranged on the right end of the piston, and the installation cover is arranged on the right end of the cylindrical groove, and the right side end of the push rod is sleeved with the handle. The novelproduct is placed in an aseptic bag for storage and use, and the mixing device is made from medical grade aseptic materials to avoid that the material itself influences patient's health. In the process of mixing drug liquid and drug powder, when the drug liquid is transported by the upper thrusting needle and lower thrusting needle, the drug liquid can not be exposed to the air to prevent the outside air from contaminating the mixed drug liquid, the drug liquid flow can be conveniently controlled, and based on the above descriptions, the device has better application prospects.