Photoacoustic imaging has been recently developed for biomedical imaging. This imaging technique is based on the photoacoustic effect, which includes a process involving the absorption of photons, the subsequent thermal expansion, and propagation of photoacoustic waves. The propagation of photoacoustic waves has been modeled by using linear acoustic theories although the generated photoacoustic waves are naturally shock waves. In this work, the propagation of photoacoustic shock waves are studied by using nonlinear acoustic wave solutions based on Hugoniot’s shock relation combining Earnshaw solution with Poisson solution. The non-linear solution is compared with the existing linear solution using the propagating waveforms for spherical wave. The simulation results show a discrepancy between the two solutions.