The security of stream cipher, which is known as one of the main cipher techniques, dependents completely on the quality of generated pseudo-stochastic sequences. Chaotic systems can produce the pseudo-stochastic sequences with the properties of excessive dependence on initial conditions and the difficulty in forecasting, therefore, these systems are suitable to the stream cipher. A new encryption algorithm is proposed by analyzing the principle of the chaos encryption algorithm based on logistic formula. Moreover, the security and performance of the proposed algorithm is also estimated. Finally, an example is given to demonstrate our method via the Visual C++.