In this paper, we propose a novel stream cipher based on a chaotic system. In order to get the cipher text, the plain text is simply XORed with the key-stream generated by a strong pseudo chaotic number generator (PCNG). Then, all the security of the system is based on the used PCNG. The structure of the proposed PCNG includes two chaotic maps which are weakly coupled by a predefined matrix and integrates a swap function. The PCNG passes all statistical NIST’s randomness tests. Also, analysis and experimental results show that the proposed stream cipher has a large key space, a high key sensitivity, and can resist against chosen-plaintext attack and chosen-ciphertext attack. Indeed, for each new execution of the system using the same secret key, the generated keysteram is different due to the IV-setup function. The computing performance of the proposed system is comparable to the main algorithms of eStream such as Rabbit and HC-128.