The accumulation of Enteromorpha prolifera in huge amount in the Yellow sea in June, 2008 draws the attention from all over the world. It is an urgent requirement to monitor the wide range of Enteromorpha prolifera distribution by remote sensing. As to the Enteromorpha prolifera floating on the sea surface, effective monitoring by optical remote sensing has been basically achieved. As far as the underwater suspended Enteromorpha prolifera is concerned, the present paper carried out the radiative transfer simulation research on the above water spectral response, its variation with the suspending depth, the water turbidity and environmental conditions. It was found that with the increase in Enteromorpha prolifera suspending depth and water turbidity as well as the decrease in the thickness of Enteromorpha prolifera, the Enteromorpha prolifera information contained in the surface spectra would decrease. The influence of environmental factors such as water-gas interface roughness, cloud cover extent and sun zenith angle on the underwater suspended Enteromorpha prolifera spectra can be ignored. The maximum Enteromorpha prolifera depth that can cause surface spectrum changes is about 30 m in clean water and about 1 m in turbidity water.