In order to understand the influence of exhaust variable valve timing （exhaust VVT） on engine power and fuel economy， a sweeping experiment was made on a natural aspirated GDI engine. The influence causing changes in engine power and fuel economy at different exhauste VVT phase angles was analzed based on the parameters of intake airflow， peak combustion temperature， indicated thermal effiency and pumping loss. The results show that delaying the exhaust VVT by 15° crank angle can enhence engine torque and intake airflow at full load and full speed， but its further delay will decrease the torque and increase the pumping loss. Using the exhaust VVT at the medium and high loads below 2 400 r/min can enhance the thermal effiency and reduce the pumping loss and fuel comsumtion. When the exhaust VVT is delayed by more than 15° crank angle ， the fuel economy will become deteriorated at the medium and high loads over 2 800 r/min.