Mu Chun was from a rich family in Jieyang Town, and the younger brother of Mu Hong. He excelled in martial arts and was particularly good in using a sabre in combat. He was nicknamed 'The slightly restrained' (小遮拦), which was quite similar to his older brother's nickname. The brothers were well-known in the town and had a great influence on the people.
Once, Song Jiang was exiled to Jiangzhou and he passed by Jieyang Town on the way. He met Xue Yong who was performing in the streets. The Mu brothers ordered the people not to award Xue with money for his performance, but Song ignored them and awarded Xue five taels of silver. Mu Chun was furious with Song Jiang and wanted to hit him, but Xue Yong came to Song Jiang's aid and he won Mu Chun in a fight.