A waste heat recovery system for an internal combustion engine for agriculture was developed. The system is for recovering both of exhaust heat and cooling heat of an engine and is so simple in its structure that can be used in rural area easily. A series of experiment was carried out to the experiment which will be discussed later on, collect data for the performance of the system at various operating conditions of the system and an engine and to determine a range of coolant temperature in which performance of an engine is not affected by the heat recovery system incorporated. The obtained experimental data is not only useful to materialize performance of the system at the experimental conditions but also to construct a mathematical model of the system to predict the system variables beyond the scope of