In the actual tracking scenarios of the CMIMO (collocated multiple-input multiple-output) radar, the high dynamic RCS(radar cross section) fluctuation characteristic is not utilized effectively and thus it will lead to low tracking accuracy or even missing tracking. To solve this problem, a CMIMO radar power resource adaptive allocation method based on the high dynamic RCS fluctuation characteristic was proposed. Note that the target RCS was sensitive to the observing angle and the actual observing angle could be obtained dynamically via the prediction of target kinetic state, thus the polarization mode could be optimized during different tracking frames. Thereafter, the tracking posterior Cramer-Rao bound which included radar transmitting power and RCS was derived and it could see as the object function to be optimized. Finally, the internal penalty function method was implemented to tackle the aforementioned optimization problem and it achieved the optimized power allocation with high dynamic RCS. Simulation results validate that compared with the traditional RCS model allocation method, the proposed method fully utilizes the dynamic RCS fluctuation characteristics to achieve the effective allocation and it solves the mismatched problem between the allocation scheme and the actual tracking scenarios, which improves the multi-target tracking performance of the CMIMO radar.