The presented paper uses the Finite Element Method (FEM) to analyze the thermal stress and distribution of three different aluminum alloys. The simulations are carried out by evaluating the parameters like gas pressure, temperature and material properties of the Piston. The four-stroke engine of Bajaj Pulsar 220CC is used to study the analysis procedure for aluminum alloy piston. The resulting analysis will give the prediction of critical region and maximum stress. It is important to locate the critical area of concentrated stress for appropriate modifications. Static and thermal stress analysis is performed by using ANSYS 14.1. The analysis result will help to choose the best aluminum alloy material. The analysis results are used to optimize piston geometry of best aluminum alloy.