Abstract: With the synthetic test data and the Hudson Canyou experiment provided by the Ocean Acoustics Library (OALIB), algorithm of mode decomposition of sound field me systematically examined in this paper, concerning (1) the effect of white noise and colored noise; (2) the tolerance of realistic environmental uncertainty and error; (3) the ability for detecting and tracking the underwater sound source. At the sometime, the localization performances of the different type of the short and sparse vertical array were discussed at lower SNR. Fortunately, this algorithm was passed successfully.