An improved coupling lattice model of two-lane traffic flow is proposed by taking into account the effect of the two-lane coupling and lane changing. And the lane changing rate of traffic flow is modified. The analysis of the modified lane changing rate shows that it is in better accordance with the real traffic than the previous ones. The linear stability condition of the extended model is obtained by using the linear stability theory. Numerical simulation also shows that our model can better reproduce the lane changing of traffic flow than previous ones by considering the information of two-lane coupling interaction. And there is unavoidable effect on the two-lane traffic flow from the coupling effect between the two lanes.