Energy flow test of internal combustion engines is an important method to evaluate energy consumption of engine under different control strategies and indicate improvement directions. The energy balance analysis based on coolant temperature was carried out on a turbocharged direct injection gasoline engine. According to the thermodynamics law, the energy balance terms consisted of useful work, cooling loss, exhaust loss and unaccounted heat loss caused by radiative heat transfer. The results show that the specific fuel consumption decreases and NO_x emission increases at low load; while HC emission decreases and CO and CO₂ emissions keep almost the same at whole working conditions with the increase of coolant temperature. The ratios of useful work and exhaust loss increase with the increase of load and are little influenced by coolant temperature. In addition, the cooling loss ratio decreases with the increase of coolant temperature.