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The classical ultrasonic level measurement method has been widely applied in process industry based on sound reflection phenomena. But this method will be harmfully affected by the parasitic reflections. On the other hand, there will be a big error if observed values are directly used to calculate liquid height because of environment noises. In order to overcome these shortcomings, a level measurement method using acoustic standing wave is presented based on particle filter. Firstly, the nonlinear state equation and linear measurement equation about the standing wave lengths are formulated according to acoustic standing wave method. And then the estimation of the standing wave length will be got to compute the level based on particle filter. Moreover, the efficiency of this method can be proved by experiments. Finally, a new ideal to decide whether the tube is blocking is shown further.