ocean surface current algorlthm based on MUltiple SIgnal Classlfication (MUSIC) is used for current mapping of Wuhan Universlty's occan state measuring and analyzing radar (OSMAR2000), in which MUSIC is applled to estimate the bearings of the first-order sea echn slgnals. The premlse of MUSIC processing is that the number of signals is known in advance. In fact, the numbere of signals is unknown, and needs to be estimated from received data. In the case of diserete larges the problem can be perfectly solved ming information theoretic criteria such as the Akalke Information Criterion (AIC) Or the Minlmum Description Length (MDL) criterion. However, these criteria are proved unsuccessful for sea echo signals both in slmulation and in actual application, since sea surface is essentially a continum. Therefore, an ad hoc method of dotection of dete number of signals, a bit different from the existent mebods, Is developed for the current algorithm of OSMAR2000. The underlying idea is to determine the number of signals based on the varlance of MUSlC spectra stracture under difierent candidate number of signals.