There are many problems in the engineering application of the current national standard and industrial standard of the rebound method for fired common brick, for instance, low accuracy, limitation of application and errors in citation. Based on the comparison of rebound testing method provided in 4 existing standards and on the mathematical statistical method, a general formula of the strength calculation for fired common brick in existing masonry was proposed, and the uniform provisions concerning the application of this method were made. The high accuracy of the general formula of strength calculation has been verified in the test organized by the Committee of National Standard GB 50315. The research will have reference value for site testing of masonry engineering, and will provide an important basis for the revision of the national standard GB 50315.