The present invention discloses an interface ultrasonic reflectivity-pressure relation curve establishment method and a loading testbed. The loading testbed comprises a force displayer, a control terminal, an oscilloscope, an immersion ultrasonic transducer, a large cylinder, a small cylinder, an upper panel, a movable plate, a force sensor, a lower panel, an ultrasonic transceiver and a small cylinder connecting plate. Compared with the existing schemes, the interface ultrasonic reflectivity-pressure relation curve establishment method and the loading testbed provided by the present invention can construct a more accurate ultrasonic reflectivity-pressure relation curve, and are high in detection precision.