Abstract: In this paper, signal preprocessing for bearing determination of ocean surface radial current mapping by HF ground wave radar based on MUSIC is investigated. oceant surface radial current mapping involves determination of the current velocities and the azimuths and range of the sea cells on which the surface currents reside. Sea echoes are firstly FMICW- demodulated to separate different range cells of sea echoes. Based on the sea echo Doppler power spectra of every channel, channel amplitude responses are software calibrated for every range cell. The first-order spectra, which contain ocean surface current information, are separated afterwards from the synthesized sea echo Doppler power spectra of every range cell. At last, the usable spectral bins for extracting ocean surface radial currents are picked out by "local noise threshold filtration method". The ocean echo signals at these spectral bins are then processed by MUSIC algorithms to obtain the azimuths of every radial current. So that the whole information for ocean surface radial current mapping is obtained. The set of algorithms in the procedure are investigated in this paper, as well as their effects and part of actual measurement results.