Abstract: Aiming at the problem that the positioning accuracy of the traditional long baseline underwater acoustic positioning model decreases significantly when taking the aircraft black box and other periodic drift acoustic beacon as the target, a new long baseline positioning model independent of the signal periodic information is proposed. The model extends the traditional delay difference location model to the second order, and eliminates the unknown acoustic beacon period by calculating the second derivative of arrival time. In order to avoid the non-convergence problem caused by the increase of order, an improved Newton iterative algorithm is introduced to effectively improve the convergence probability of the new model. The positioning errors of the simulation experiment and lake test experiment of the new model are 3.14m and 1.19m respectively. The experimental results show that the model realizes the high-precision positioning solution of periodic drift acoustic beacon.