A distributed weighted fusion algorithm was presented based on interacting multiple model and unscented Kalman filter (IMM-UKF) in context of radar / IR combined guidance maneuvering target tracking for the problem that divergence prone to occur to filter in nonlinear maneuvering target integration tracking. IMM is capable of adaptively tracking different target maneuver mode. UKF was introduced to obtain state estimation to avoid calculating Jacobian matrix and overcoming EKF's disadvantage of dependence on initial value and divergence. Distributed fusion algorithm was introduced to improve anti-jamming capability and effectiveness of target tracking and tracking accuracy. Simulation results show that the algorithm can reduce errors of maneuvering target tracking fusion result, improve the accuracy of target tracking filter and enhance the stability of the system in the treatment of non-linear system.