Numerous spectroradiometric measurements were carried out in the Caofeidian offing and, on such a basis, correlation was made between the average reflectance and the concentrations of surface suspended particulate matter (SPM). The empirical relationships were established between remote-sensing reflectance (Rrs) in TM-HRV bands and SPM concentrations. The results show that the remote-sensing reflectance increases with SPM concentrations. When the SPM concentrations are lower than 20 mg/L, the amplitudes of remote-sensing are wider in the 570 nm than in the 670 nm, but when the SPM concentrations are higher than 20 mg/L, things are just the opposite. The best correlations are obtained for Rrs (TM3) and SPM concentrations, which show remarkable exponential correlations. As a result, SPM concentrations within the surface waters in Caofeidian offing are estimated with an average accuracy better than ±28%.