Abstract: During sea-state remote sensing by skywave OTH radar, the received sea-surface echoes may be smeared by the ionospheric slow phase-path modulation. Furthermore, it worsens also sea-state parameter estimation. In this paper, by taking advantage of known knowledge of sea-state remote sensing about the first-order Bragg lines, the existing algorithm estimating the ionospheric slow phase-path modulation is optimized for better sea spectral estimation. Simulation shows the advantages of the optimized algorithm in sea-state parameter estimation.