Abstarct: Natural gas is entered in CNG stations for vehicle using. CNG stations are placed including continous equipments. These equipment were designed as they transfer natural gas to vehicles by high pressure and safely. In CNG stations, gas with pressure 1.5 MPa is received from urbon gas pipes. In order to using in vehicles, its pressure increase to 25 MPa. In CNG stat ions, compressors are the heart of station due to compression of natural gas. These compressors are commonly reciprocating type which knows as piston cylindrical compressors. In precent research, the role of reciprocating compressors in CNG stations is firstly investigated. In the next section, reciprocating compressors, mechanism, main designs as well as their different component is studied. Then, the number of state equation usable for natural gas described. More, the AGA8 state equation as well as their relationships using in thesis are comprehensively introduced. Further, simulation of reciprocating compressore and their governing equations as well as solution algorim are explained for ideal and real gases. Finally, gas compression process at various steps accompanied by related curves are investigated for ideal and real gases. Also, compression process for gas composition exiting in different gas field is studied. The MATLAB software is utilized in this research.