An encryption method based on turbo code is proposed in this paper. In the scheme, we adopt an improved interleaver for turbo code. The new interleaver has two characteristics: (a) It provides low correlation for information bits in one turbo frame, which means better error correction capability for short turbo code; (b) The output of the interleaver is controlled by the secret key, therefore the function of information encryption can be achieved. In order to enhance the security of encryption, an outer interleaver based on DES is applied. By these means, the high error correction capability of turbo code can provide good immunity to the transmitting errors for the encryption method. Simulation shows that the proposed method has good security and error-immunity performance simultaneously.