Abstract: The flexible horizontal array carried by the receiving base in the bistatic base of active mode has real-time array shape distortion during the motion. The detection performance of hydrophone arrays is seriously affected by the existence of array shape errors. A method is proposed in this paper to estimate the array shape parameters using direct waves based on LFM signal to solve the problem. In the method, the FRFT is firstly used to separate the direct wave from the target echo, avoiding the influence of the target echo on the array parameter estimation. The phase difference between the corresponding peak points after FRFT of each array element is used to estimate the array parameters, and an array deblurring method based on the radiation noise of the towing vessel is proposed. Computer simulation shows that the method is tolerant to noise and interference effects, incident angle errors and Doppler shifts. The effectiveness of the array estimation method is verified by the experiments on the lake, which is a flexible horizontal array estimation algorithm that can be calibrated in real time with high accuracy and robustness.