The nonlinear regression and fitting analysis for the modulated wareform of pressure wave on the reheater of pulse tube refrigerator is presented. The solitary wave in the form of hyperbolic secant was gotten, which affirms experimentally that the modulated wave is the solitary wave's solution of K-dV wave equation induced from gas dynamics equation set of non isoentrope process. It gives support to solitary wave refrigeration mechanism of pulse tube refrigerator.