A system and method for generating analog-digital mixed chaotic signal and a encryption communication method thereof, by the means of the complementary characteristic of the continuous chaotic system (12,22) and digital chaotic system (11,21), the shortcoming that the continuous chaotic system (12,22) cannot steadily and synchronously work for long time and the synchronous signal must be transmitted in channel will be overcame, meanwhile the problem, i.e. the characteristic degenerate of the digital chaotic system (11,21) will be overcame. By the present invention, the digital chaotic systems (11,21) separated each other control local continuous chaotic systems (12,22) respectively, so as to enable the continuous chaotic systems (12,22) separated each other to steadily and synchronously work for long time without transmitting the synchronous drive signal and increase the capacity for preventing from the attack effectively; the continuous chaotic systems (12,22) disturb the local digital chaotic system (11,21) to prevent the digital chaotic system (11,21) from the characteristic degenerate. The digital chaotic sequence output from the analog-digital mixed chaotic system (1,2) can be as the pseudo random number sequence, or as the privacy key stream to encrypt the data; and the continuous chaotic signal has been output can be used to design the chaotic-synchronous based secrecy communication system.