Abstract：Whether thermal condition of cylinder head is normal or not is one of important factors to evaluate Engine’s reliability performance. Based on infrared temperature measurement technology, the correlative rule of outer surface temperature field of cylinder head with working condition of engine was studied on one certain diesel engine. Combined with simulation calculation, characteristic temperature field distribution was developed on outer surface of cylinder head. The results showed, simulation values were well matched with experimental values. Under same structure and heat transfer condition of cylinder head, the thermal condition performance of engine can be described by outer surface temperature values, which provides a new gist for monitoring thermal condition of cylinder head on-line. Furthermore, applied infrared temperature measurement to engine has a widely foreground.