Aimed at SAR raw data, this paper proposes a high capacity information hiding algorithm based on pixel pair matching conducted according to the secret data. By using an extraction function, different combination of SAR real part and imaginary part are mapped into a secret digit in an n2-ary notation system, and the optimal combination is chosen for a data block with the smallest MSE. Thus, the distortion caused by information hiding can be ignored for SAR imaging. Compared with the other similar algorithms, the PSNR of the proposed method increases 0.7 dB on average under condition of the same capacity, and high security is achieved with the help of various combinations.