A Stirling engine is a heat engine operating by cycle compression and expansion of air or other gas stirling engine is a new generation of stirling engine that has been born to increase the effectiveness of stirling engine .this engine is noted for its high efficiency compared to another engines. This compatibility with alternative and renewable energy sources in which it has become increasingly significant as the price of conventional fuels rises, and also in light of concerns such as peak oil and climate change . this paper is mainly aimed to analyze stirling engine as a LTD or practical engine which has high efficiency almost nearer to the carnot cycle based engine .As a result , this study indicates how stirling engines work and give the higher efficiency than present time engine.