The invention provides a method for evaluating full-polarized SAR isolation degree based on distributed targets. The method obtains a ground feature, reversely adds crosstalk to the actually measured scattering matrix of the selected ground feature, obtains the estimated value of the SAR crosstalk by using a correlation coefficient between channels, so as to reflect the isolation degree of the polarized channel of the polarized SAR. The method mainly solves the estimation of the polarization isolation degree in the full-polarized SAR quality evaluation, and comprises main steps of: selecting a ground feature, dividing the actually measured scattering matrix of the selected ground feature, namely data M to be evaluated, into N data blocks MN with the same size; reversely adding crosstalk [delta] to the data blocks MN, and computing the correlation coefficients [rho]HHHV, [rho] HHVH, [rho]VVHV, [rho]VVVH between the co-polarized channel and the cross-polarized channel under different [rho]; acquiring the added crosstalk values which minimize the correlation coefficients [rho]HHHV, [rho] HHVH, [rho]VVHV, [rho]VVVH for each data block; subjecting the 4N crosstalk values to statistical averaging to obtain the crosstalk estimated value, and taking the negative value of the crosstalk estimated value as the polarized channel isolation degree.