The invention discloses a master-slave integrated mechanical arm for assisting minimally invasive surgery. A master operating end of the mechanical arm comprises a master hand joint I seat provided with a rotatable master hand joint I shaft; the output end of the master hand joint I shaft is connected with a master hand joint II seat; the master hand joint II seat is internally provided with a rotatable master hand joint II shaft which is fixed with a telescopic frame; an upper telescopic seat is connected with a lower telescopic seat by a linear mechanism; a slave operating end comprises a base part connected with the master operating end, a driving mechanical arm part connected with the base part and a telescopic part installed on the driving mechanical arm. A tool clamping end comprises a surgical instrument seat installed on a slide block of a slave hand telescopic part; the upper surface and the lower surface of the surgical instrument seat are respectively fixedly connected withtwo ends of a transmission screw and can move in a straight line along the guide rail of the slave hand telescopic seat under the traction of the transmission screw. By utilizing the device, the system structure is simplified and the system volume and the failure rate are reduced.