Abstract: Abstract Based on satellite data of sea surface temperature and salinity at Southeast coast and the Western Pacific, dual-Debye model and M-G mixed media theory with foam are applied to calculating sea effective permittivity, analysis shows that different area changes in temperature and salinity will have great impact on imaginary part of permittivity at P/L-band and have little impact on other bands, where the affecting of permittivity on a given frequency sea scattering coefficient has the range of only 0.1dB, thus the sea condition and state are of significant importance. Based on the modified two-scale model and VRT, considering the cut-off wavenumber at different frequency and sea states, numerical results show the low grazing angle electromagnetic backscattering at multi-band (P/L/S/X/Ku-band) in different sea area, and the affection of wind speeds and directions, foam cover, frequencies and polarization are considered at the same time. The mechanism of multi-scale low grazing angle electromagnetic scattering is also analyzed.