Abstract: According to the in-situ measurement of damage shape ofimpacted object and the theory of direct back analysis, the magnitude of theimpact load and the dynamic tensile strength for laminar rock plank areidentified by taking the similitude-degree between the measured damageshape and thenumerical simulated shape as the target function. The analysis method iseffective for some ancient architectures, especiallywhen the initial information and measurement data, are scare.