In the presence of non-gaussian noise, we propose a method for the detection of underwater shipradiated signal. The wavelet decomposition of the underwater signal yields a natural tree structure, which is further modeled by the Hidden Markov Tree (HMT). Therefore, the signal is represented as the parameter of the correspondent HMT. We analysis the likelihood defined on the parameters and form the new detection criteria. Experimental results demonstrate a reliable and robust solution of our method.