Abstract: Firstly, in the framework of the Interacting Multiple Model (IMM) algorithm the constant-velocity model and the adaptive constant acceleration model are selected as the dynamic models for the un-maneuvering and maneuvering states of the un-cooperative target, which is called the adaptive IMM algorithm. Then since it is necessary to consider the performance of estimating range/velocity and Doppler tolerance for tracking a maneuvering target, the V-Linear Frequency Modulated (V-LFM) signal is selected as the transmitted signal in the radar system. The analysis on the Cramer-Rao Lower Bound (CRLB) for estimating the range/velocity and Doppler tolerance of three signals (LFM, V-LFM and M sequence) shows that the V-LFM waveform can effectively improve the performance of estimating the target range and velocity in the case of a bit loss in the Doppler tolerance. The simulations demonstrate that the tracking performance is apparently improved, when multiple pulses of V-LFM waveform is transmitted and the adaptive IMM algorithm is utilized in the radar system.