During walking， interaction between patient and exoskeleton determines safety， comfort and performance of patients using the exoskeleton， which thus has attracted extensive attentions in related research of rehabilitation exoskeleton. In this paper， the wearable lower limb rehabilitation exoskeleton is investigated with the coupling effect between patient and exoskeleton being considered. The human-machine interaction force model is given with influences of foot-ground contact force being taken into account and thus the human-machine coupled dynamic model is established based on Lagrange equation of the first kind. Furthermore， considering the characteristics and actual needs of patients in different stages of rehabilitation training， corresponding control strategies are given. In particular， in active stage of rehabilitation， the actual physical interpretation of the reference trajectory correction in the exoskeleton position impedance control based on human-machine interaction force is given from the perspective of human-machine interaction dynamic model， and the impedance control PID controller is designed. The simulation results show that the human-machine interaction forces can be analyzed effectively by using the human-machine coupled dynamic model. Furthermore， the control strategy designed in active stage of rehabilitation training can effectively reduce the level of human-machine interaction force on the basis of ensuring a certain trajectory tracking accuracy.