In this study, temperature distribution and total heat transfer were calculated for two-dimensional cross flow heat exchanger using finite difference method. A cross-flow heat exchanger consists of parallel sheets. While the hot fluid flows from one plate, the cold fluid flows through the next plate with cross geometry. This structure is repeated in many plates. After the differential equation is converted to the finite difference equation, it proceeds in a row by starting from the corner where the two inlet temperatures are known, and thus the temperature profile of the entire heat exchanger is easily reached. Throughout the study, air was used as cold fluid in all analysis. Air and exhaust gases were taken as hot fluid, thus the performance of the heat exchanger was examined. A mathematical model was developed by using the finite difference equations in Java programming language. For example, the temperature profile of a hot air with an inlet temperature of 75 C and the temperature profile of a cold air with an inlet temperature of 20 C were calculated with the aid of the mathematical model and the total heat transfer was determined approximately 45,5 KW.