Abstract: In order to solve some problems in the bag filter such as the uneven distribution of the inner flow field，exceeding hith velocity of flue gas near some points of the bag，the Fluent software is used to numerically simulate the internal flow field of bag filter， and a new kind of composite guide plate was set inside the bag filter． The result of numerical simulation shows that the average velocity and the axial velocity of the flue gas which flow into the bag-type strainer area decrease sharply after the composite guiding plate is set up． At the same time，the internal flow field distribution becomes more homogeneous． This could provides a reliable structure improvement method for bag filter．