A numerical simulation model for a pulsed laser induced ultrasonic in a diamond anvil cell (DAC) is established by using finite element method (FEM). The transient temperature field and ultrasonic displacement field in sample under high pressure are simulated. Ultrasonic waveforms at different positions in the rear face of sample under the irradiation of a vertically incident laser pulse are obtained, and the characteristics of ultrasonic displacement field changing with time are analyzed. The numerical results show that, ultrasonic wave generated in thermoelastic effect has obvious directionality in a DAC. The energy of longitudinal wave is concentrated near the laser incident direction, and the energy of shear wave is concentrated between 30° and 55° that deflects from the laser incident point. The characteristics are different from the results of free surface in thermoelastic effect, but they are similar to the results of free surface in ablation effect.