The function relation between polarization and the density of seawater at the range of visible waveband can be established by index of refraction,but there is a great calculation error.In order to calculate the density of seawater more accurately,the best waveband of calculating the density of seawater was determined based on dispersion theory.Seawater from Dalian Bay and Yueya Bay was used as study objects,and USB2000 spectrometer was used to measure the polarized spectrum of seawater,and then its polarization was calculated.Iterative inversion was used to find out the waveband which has the smallest polarization errors that match along with the actual density,which means the optimal waveband of calculating the density of seawater.The results show that seawater with different densitis has different optimal wavebands to calculate the densities at different incident angles.That is to say,the calculation of density has a higher accuracy at the range of (650±2)-(670±2) nm waveband.A further step of using polarization information to calculate the density of seawater in the practical application of remote sensing technology is showed.