Abstract: This paper introduces encode and decode principle of Turbo code.Owing to the disadvantage that traditional stopping criteria expend hardware resource too much，uses the combination of cross entropy criteria and exterior information by way of the stopping criteria.The result of simulation indicate that the new stopping criteria can guarantee the number of iteration and decoding capability under the circumstance of difference of Signal-to-Noise；it can increase the quality of digital wireless transmission，reduce the system delay and save hardware resource furthest by using this algorithm.

Key words: turbo code, stopping criteria, cross entropy criteria, exterior information

摘要： 介绍了Turbo码编码与译码原理。针对传统停止迭代准则译码耗费硬件资源的不足，提出了利用外部信息结合交叉熵迭代停止准则作为新的迭代停止准则算法。仿真分析结果显示：新的迭代停止准则可在不同的信噪比情况下，保证迭代次数适中并确保译码性能的稳定，应用该算法既可提高无线通信的数据传输质量、减小系统传输时延，又可最大限度地节约硬件资源。

关键词: Turbo码, 迭代停止准则, 交叉熵准则, 外部信息