Making use of one-dimension heat exchange and Navier-Stokes(N-S) equations,the stress pulse that is brought by laser is researched by using simplification sinusoid pulse model.Experssions of the stress pulse are attained,whose sample is feeble absorbability and its surface is free or tightened.The results show the sinusoid pulse model and the popular model have the same conclusion,and the extent of ultrasound stress pulse depends on the optical and thermal characteristics and thickness of the sample.Also it is much closer to true skew-Gaussian laser pulse,and it shows universality.