Because the pre-existing model of bidirection two-lane mixed cars traffic flow has something doesn’t accord with the actual factors, and unreasonable lane-changing rules may result that the lane-changing vehicles are not able to return to its course so that causes jamming. we consider canceling the restrictions on the queue of low-speed car, combine with FI model, and think when the car is changing lane, the behind vehicles from its adjacent lane have effects on it. The concept about the rear security gap from adjacent channel, the deceleration avoid mechanism and the proportional parameters of mixed car are all introduced, we proposed a new bidirectional two-lane traffic flow model. The fundamental diagrams of the new model are acquired by carrying out numerical simulation, and compares it with the pre-existing model. Furthermore, we studied the system characters of the new model from free flow to the maximum flow, or the blocking phase, as well as the coupling effect of the two lanes. The results show that the new model is more conducive to improve traffic jam, and enhances the utilization of the road; Under different injection and vanishing probability, the critical point of system is different, the system characteristics also had a significant changing; Meanwhile, for the different vehicles mixing ratio, the basic characteristics of the traffic flow is consistent but critical value is different; The emergence of low-speed cars in the mixed traffic flow play a dominant role, and influence on the entire traffic condition.