The ultrasound generation mechanism was analyzed under ablative mechanism.The finite element model of a workpiece was established.The impact force of plasma on the material was taken as the ultrasound drive source.The propagation process of laser ultrasound was simulated in workpiece.The time course curve of node placement was calculated,and the speed of an ultrasound was calculated,and then the type of an ultrasound was determined.In addition,the field distribution of laser ultrasound was analyzed.The measuring contrast experiment of laser ultrasound was done by using semicircle aluminum block.In contrast experiment,the longitudinal wave,shear wave and surface wave were received by ultrasound transducer.The results of contrast analysis show that the results of numerical analysis are consistent with the experimental data,and the finite element numerical simulation method is accurate and reliable.