The invention provides a measurement device for average corrosion depth in X-ray stress testing.The measurement device comprises a support, a supporting rod and a dial gauge.The support is a U-type hollow bent part with a downward opening, the supporting rod is a hollow straight rod, the upper end and the lower end of the supporting rod are connected with the center of the top of the support and the center of the bottom of the dial gauge, a balance plate is horizontally arranged inside a cavity in the top of the support, the center of the balance plate is connected with the support through a pin shaft, a rotating spring is arranged on the balance plate, three sleeves are evenly arranged on the bottom surface of the support at intervals, the center of the top face of the balance plate is connected with the bottom end of a main spring, the top end of the main spring is connected with the dial gauge, the bottom face of the balance plate is spaced evenly and connected with the top ends of three auxiliary springs, spheres are arranged at the bottom ends of the auxiliary springs which are sleeved with sheaths, the bottom ends of the sheaths are fixedly connected with the spheres, the three auxiliary springs and the three sleeves are arranged correspondingly, and the sheaths are inserted into the sleeves and can slide along the sleeves.On the premise of guaranteeing testing precision, the average depth of a corrosion pit is tested in a one-off mode, and working efficiency and accuracy are substantially improved.