Turbo decoding has large iteration delay. Based on tail bits of turbo codes, a low-complexity adaptive iterative decoder is proposed for turbo codes in this paper. In the proposed algorithm, tail bits work as CRC bits to detect whether the decoding succeeds or not. From simulation results, the new algorithm reduces average iteration times, compared with turbo decoding with fixed iterations. At the same time, it achieves better performances of BER, FER and average iteration times for short frame size and similar performance for medium frame size without additional overhead bits or computation complexity, compared with CRC based adaptive iterative turbo decoder.