A medication mixer, comprising a base, a medication mixing passage and a medication mixing cup which are integrally formed, and a cross needle, wherein the medication mixing cup consists of a cup wall and a cup bottom; the cross needle consists of an integrated needle plate as well as an upper needle and a lower needle with hollow passages which are communicated with each other; wherein the lower end of the medication mixing passage penetrates through the base, with the upper end penetrating through the cup bottom, a separating membrane is arranged in the medication mixing passage between the base and the cup bottom, and a rubber plug is arranged in the medication mixing passage between the separating membrane and the cup bottom; the distance of the upper surface of the cup bottom to the lower surface of the separating membrane is less than the length of the lower needle; the medication mixer further comprises a sealing membrane connected at a cup opening of the medication mixing cup in a press welding way, so as to seal the medication mixing cup; the sealing membrane is an easy-to-tear membrane which can still be basically kept smooth after moist heat terminal sterilization; characterized in that further comprising an elastic clamping base including a clamping ring provided with an elastic clamping jaw at the lower side, the upper ends of the elastic clamping jaw are arranged uniformly and fixed along the clamping ring, and the lower ends of the elastic clamping jaw are free ends, and the elastic clamping jaw inclines towards the center of the medication mixing cup from the fixed upper ends to the free lower ends; the needle plate is mounted below the elastic clamping jaw in the medication mixing cup; a limit structure is arranged on an inner wall of the cup wall, the elastic clamping base is mounted in the medication mixing cup and is limited by the limit structure; the medication mixing cup is prefilled with a certain amount of liquid before sealed by the sealing membrane, for substantially balancing the air pressure inside and outside the medication mixing cup; the liquid can be vaporized rapidly in an environment of moist heat sterilization. the cross needle consists of an integrated needle plate as well as an upper needle and a lower needle with hollow passages which are communicated with each other; wherein the lower end of the medication mixing passage penetrates through the base, with the upper end penetrating through the cup bottom, a separating membrane is arranged in the medication mixing passage between the base and the cup bottom, and a rubber plug is arranged in the medication mixing passage between the separating membrane and the cup bottom; the distance of the upper surface of the cup bottom to the lower surface of the separating membrane is less than the length of the lower needle; the medication mixer further comprises a sealing membrane connected at a cup opening of the medication mixing cup in a press welding way, so as to seal the medication mixing cup; the sealing membrane is an easy-to-tear membrane which can still be basically kept smooth after moist heat terminal sterilization; characterized in that further comprising an elastic clamping base including a clamping ring provided with an elastic clamping jaw at the lower side, the upper ends of the elastic clamping jaw are arranged uniformly and fixed along the clamping ring, and the lower ends of the elastic clamping jaw are free ends, and the elastic clamping jaw inclines towards the center of the medication mixing cup from the fixed upper ends to the free lower ends; the needle plate is mounted below the elastic clamping jaw in the medication mixing cup; a limit structure is arranged on an inner wall of the cup wall, the elastic clamping base is mounted in the medication mixing cup and is limited by the limit structure; the medication mixing cup is prefilled with a certain amount of liquid before sealed by the sealing membrane, for substantially balancing the air pressure inside and outside the medication mixing cup; the liquid can be vaporized rapidly in an environment of moist heat sterilization.