Abstract: In order to study mode conversion of laser-excited shear waves interaction with the side of vertical cracks, the laser-generated ultrasound propagating along the horizontal surface and received on the vertical surface was simulated by means of finite element method. After experiments, the change of displacement signals received by side receiving point at different depths was analyzed when laser-excited ultrasonic was transmitted to the vertical side. The results show that, when the side receiving point is within the corresponding depth of the critical angle, the surface wave signal generated by laser-excited surface wave at the secondary source of the corner appears. When the side receiving point is outside the critical angle, there is a mode transformation generated by laser-induced shear wave acting on the side of the vertical crack, and a new surface wave is formed. Furthermore, when the excitation position is fixed, time difference of arrival between both signals increases gradually with the downward receiving position. The results can promote the detection of vertical cracks by laser ultrasound.