六群比丘（以下簡稱六群）是佛教史上頗惹爭議的人物，他們既通世情佛理，卻又屢屢違犯律制，故被貶稱為「惡比丘」。可是，近世學人轉以六群的行徑為方便施設，言其旨在令律制更趨完備，六群遂搖身一變成為正面人物。而在眾律藏中，惟「根有部律」清楚舉出六群的身分，同時包含更多的相關記載。本文以漢譯「根有部律」作為基本資料，分三組八類，挑選一些事例作討論，指出六群雖具備相當的律學知識，但他們或固執條文，或挑剔刁難，往往令人討厭難堪。此諸多看似乖張的行止，暴露了僧團運作的毛病和戒律的漏洞，亦令律制得以不斷完善，從中顯示出初期佛教中道和寬容的精神，為佛教律制發展史上值得留意的一章。

The group-of-six-monks (abbreviated as “the group-of-six” thereinafter) is quite controversial personage in the history of Buddhism, whose are always denounced as “bad monks” , as they often go against the precepts. However, some Buddhist scholars nowadays re-interpret their misbehaviors as expedient, which make rooms for the Buddha to prescribe or fine-tune the rules and regulations. Among various Vinayas, only the Mūlasarvāstivāda-vinaya clearly provides the identity of the group-of-six and has abundant relevant information. Based on the Chinese Mūlasarvāstivāda-vinaya, this article divides three groups and eight items, selects some examples for discussion, in order to show that the group-of-six have considerable knowledge of monastic discipline, but they stick to the literal meaning of the precepts and challenge other colleagues. As a result, some flaws of the Sangha order and loopholes of the precepts are revealed and given a chance for continuously improvement. Hence, it has showed the middle path and compassion of primitive Buddhism. As such, this is a noteworthy chapter in the development history of Buddhist monastic discipline.