The paper Puts forward a novel feedback chaotic block cipher algorithm based on external key control. The prominent advantage of the algorithm is that the cipherkey of the system is composed of 128-bit external keys. The system parameters, initial conditions and iterations of the chaotic system generate dynamically in line with the ciphertext feedbacks. In this way, the randomness and complexity of the cryptosystem have been greatly improved. Meanwhile, theories and experiments have also shown that, the algorithm has higher security and robustness, and can resist the differential cryptanalysis and linear cryptanalysis.