Stirling Cryocoolers serve in a number of advanced technological applications to cool a variety of important components, such as infrared (IR) detectors, high temperature super conductors (HTSC), and cryogenic catheters. With the advancement in applications of cryocoolers, several simulations of such cryocoolers were also developed. These types of simulations can save a lot of time and money as it provide an accurate analysis of the performance of the cryocooler before actually manufacturing it. In this study, the commercial computational fluid dynamic (CFD) package Fluent and Gambit was utilized for modeling the entire Stirling cryocooler that includes a compressor, an after cooler, a transfer tube, a regenerator that is represented as porous medium and cold and warm heat exchangers. The regenerator is the key element of Stirling cycle cryocoolers. It can be seen that enactment of the regenerator straightly affects the cryocooler performance. Therefore, any improvement on the regenerator will lead to a more efficient cryocooler. This project represents completely new type of numerical computational fluid dynamic (CFD) approach for making it more realistic to the porous media inside the regenerator of a Stirling refrigerator. The available commercial software package FLUENT which is used for solving Computational fluid dynamics (CFD) has the capability to define a porous media and to solve the governing equation for this region.