The invention discloses ultrasonic department coupling agent smearing apparatus for preventing cross infection. The smearing apparatus comprises a coupling agent storage box, a sealing cover, a smearing head, a push rod and a protective shell, wherein the upper end of the coupling agent storage box is in threaded connection with the sealing cover, a telescopic rod is arranged at the lower end of the coupling agent storage box, the inside structure of the telescopic rod is of a hollow structure, the smearing head is arranged at the bottom end of the telescopic rod, a connecting rod is fixedly connected with the upper surface of the smearing head, a control valve is fixedly connected with the top end of the connecting rod, sliding pieces are arranged on two sides of the control valve, and one ends of the two sliding pieces are fixedly arranged at the side edge of the coupling agent storage box. Through the arranged control valve, the opening and closing of the bottom end of the couplingagent storage box can be controlled by the position movement of the control valve, and a residual coupling agent can be discharged, so that the cross infection, and the influence on the next use of aprobe after solidification of the residual coupling agent are prevented.