This paper focuses on the parameters identification for time varying structures. Based on B-spline wavelet on the interval，time varying multi-variable auto regressive model is established and the parameters identification procedure is deduced for structural instantaneous frequencies using multi accelerations responses signals. The simulation study is performed based on a three degrees-of-freedom time varying dynamic model. The structural instantaneous frequencies (periodically varying, abruptly varying and smoothly varying) are identified based on the proposed auto regressive model using the structure acceleration responses data with Gauss white noise, in order to verify the anti-noise ability of this identification method. At last, a confirmatory test is carried out using a cantilever beam with time varying mass characteristics. The first three instantaneous frequencies are identified well and the results of the experiment demonstrate that the proposed method has very good validity, efficiency and anti-noise ability.