The invention relates to an automatic knocking robot detection system for detecting flaws in a building structure. The automatic knocking robot detection system comprises a moving module, a control module, an electromagnetic knocking-type flaw detection module and a laser ranging sensor, wherein the moving module comprises a vehicle frame, two wheel frames, four groups of magnetic wheels, two groups of batteries and battery fixing plates, and each group of magnetic wheels comprises eight sheets of strip magnets, one wheel, a right-angle motor and an encoder; the electromagnetic knocking-type flaw detection module comprises a direct current motor, a push rod, a push rod spring, a push-pull type electromagnet, two guide L plates, a nut sleeve, a screw rod, a limit screw, a sensor bracket anda sound sensor; and the control module comprises an analog-to-digital conversion unit, a main control unit, a wireless communication unit, a GPS unit, a motor driving unit, a solid-state relay and aninertial navigation unit. The automatic knocking robot detection system has the characteristics of flexible detection mode, small volume, high maneuverability, more comprehensive detection and the like.