Abstract: The subcodes of binary self-dual codes whose length n between 22 and 30 and minimum distance six are studied by using of a random search algorithm，and the subcodes of dual distance 3，4，5 and 6 of these self-dual codes are constructed.The code chains of these self-orthogonal subcodes and the S-chains obtained from the dual of these self-orthogonal subcodes are also determined.According to Steane’s construction，some very good quantum codes of distance five and six are constructed by the obtained S-chains，and some of these quantum codes have improved parameters than previously known codes.

Key words: self-orthogonal codes, self-dual codes, S-chains, quantum error-correcting codes

摘要： 用随机搜索算法研究了码长n满足22≤n≤30且距离为6的二元自对偶码的子码，构造出它们的对偶距离为3、4、5和6的子码的生成矩阵。研究了这些子码构成的码链以及它们的对偶码构成的码链。利用所得到的码链，由Steane构造法构造出距离为5和6的具有很好参数的量子纠错码，改进了前人得到的几个量子纠错码的参数。

关键词: 自正交码, 自对偶码, 码链, 量子纠错码