Taking the sample structure of an electronic injector used in intake manifold gasoline injection system as an object,the magnetic circuit structure was redesigned by adding a magnetic isolation sleeve to improve its dynamic response characteristics.The finite element model of the injector’s magnetic circuit was established with the help of Ansys software circumstance,and the parameters of the yoke iron and sliding air gap were improved based on the electromagnetic field simulation results.The dynamic characteristics and flow characteristics of the injector before and after improvement were compared by test.The results show that the open delay time is shortened by 0.28 ms,the close delay time is shortened by 0.14 ms,and the average dynamic flow rate is increased by about 1.8 mg.In addition,the fuel mass injected at different injection pulse is larger than that before improvement.