Observers based on set value theory (SVO) have a good performance in the maneuvering target tracking (MTT) problem. By assuming system disturbances, are unknown but bounded (UBB) the SVO or UBB filters can be used in maneuvering target tracking (MTT) problems. In the UBB filter implementation, free parameters appeared when bounding ellipsoids are used. Inappropriate choice of these free parameters, reduce accuracy and caused filter instability. To solve these problems, two methods (recursive parameters calculation (RPC) and calculates the optimal free parameters (OPC)) will be developed. Free parameters that calculated with OPC method, improves the accuracy of maneuvering targets state estimation and avoid algorithms instability in the MTT problem. The results of numerical simulations, confirms improved the efficiency and accuracy of the UBBF filter by using OPC method for free parameters calculation.