The traditional sound broadcast system of bus makes use of MPU. It's shortcoming is have lower dependability, at the same time the maintenance and upgrade is difficult. In order to solve these problems, an intelligent sound broadcast system of bus makes use of Complex Programmable Logic Device(CPLD) and sound chip ISD2560 is introduced, and the principle of design is analysed. Because of the ability of In System Programmability of CPLD's JTAG, and take full advantage of the resource in CPLD, this system have no use for MPU. So, the hard circuit of this system is simple, and the system is easy to debug, upgrade and has very high dependability and better practicability.