Abstract: Under complex ocean environment,the acoustic channel is a random channel in space-time domains,Because of this fact and the mobility of underwater carriers,many measuring samples that deviate from the true trajectory can be obtained in underwater positioning system,and lead to the worse smoothness of measurement.A real-time data processing and recursive algorithm,which gets rid of error trajectory samples automatically for Kalman filter,is proposed to solve the problem of filtering instability.The reciprocal of distance D is selected as a state variable,and 1/D is considered changing linearly.So the error of measuring equation is linear,the Kalman filter can continue operating stably with unbiased estimation.Using a recursive Kalman filtering method,calculating filtering gain matrix K_k beforehand,fixing the value of Q_k and R_k,and getting rid of error trajectory samples automatically by setting threshold,as a consequence,can make the filter operation convergent and stable in a short time with good performances in aspects of real-time processing and accurately tracking ability to high speed targets.