The invention provides a mechanical arm for urinary surgery operation. The mechanical arm comprises a pedestal, a mechanical arm rotating mechanism, a rotating arm mechanism, a thick tube feeding mechanism, a thick tube rotating mechanism and a thin tube feeding mechanism. The mechanical arm rotating mechanism is fixed on the pedestal and is provided with a rotating boss; the rotating arm mechanism comprises a first rotating arm, a first motor, a second rotating arm and a second motor; the rear end of the first rotating arm is hinged to the rotating boss and a hinge joint shaft is fixedly connected with an output shaft of the first motor; the rear end of the second rotating arm is hinged to the front end of the first rotating arm, and a hinge joint shaft is fixedly connected with an output shaft of the second motor; the front end of the second rotating arm is in hinged joint with the thick tube feeding mechanism; the thick tube feeding mechanism is connected with the thick tube rotating mechanism; the thick tube rotating mechanism is connected with the thin tube feeding mechanism. The mechanical arm for urinary surgery operation has the advantages that the mechanisms can output specific movements to replace surgery tool operation of arms of surgery doctors, so that the labor intensity of doctors is reduced and accurate and standard surgery is achieved.