The improvement of the generation efficiency has attracted much attention, confronted with the little amplitude of acoustic wave generated by pulsed laser in the thermoelastic regime. This paper constructed the finite element model to simulate ultrasonic waves generated by the ring-shaped laser source with the 8 mm inner radii. The numerical results demonstrate that strong focusing exists at the center axis of ring as the result of constructive interference of the waves generated by different parts of the source. Furthermore, the bulk wave includes compression, shear peak amplitudes and the surface acoustic wave magnitude drops quickly when the receiver position is away from the epicenter. Numerical simulations indicated that the low acoustic amplitudes in laser acoustics can be relieved somewhat by taking advantage of constructive interference between waves generated by different parts of an acoustic source, giving locally higher amplitude.