This paper proposes a lossless (m, n) secret sharing method based on Thien and Lin's method. First, a secret image is scrambled by the toral automorphism technique to enhance the security and then the scrambled image is shared into n shadow images by the proposed method. The secret image can be reconstructed if subset m (1< m les n) of the shadow images are obtained. Experimental results show that the proposed method is feasible for sharing image.