Integrating Multi Protocol Label Switching (MPLS) and Mobile IP (MIP) protocols is a challenge to support Quality of Services (QoS) as well as mobility. Existing approaches may suffer from (1) high blocking rate and handover delay due to the path re-establishment, and (2) twice MPLS label PUSH and POP procedures due to the triangle routing. In this paper, we propose a novel approach to integrating MPLS and MIP. The proposed approach maintains an efficient QoS path and solves the above drawbacks. We also design a path extension procedure to reduce blocking probability and a path optimization procedure to maintain the shortest transmission path under delay constraints with the lowest cost. The simulation results show that the proposed approach reduces handover delay, connection dropping rate, and data loss rate comparing to the original MIPs over MPLS. Furthermore, we can also tune the system performance using an extension counter for the trade-off between management cost and data transmission delay.