Suzhou, Anhui
It is not known when Zhu Xuan was born, but it is known that he was from Xiayi (下邑, in modern Suzhou, Anhui). As of 882, he was serving under Cao Cunshi () the military governor of Tianping Circuit, when Cao was killed in battle when Tianping came under attack by Han Jian the military governor of neighboring Weibo Circuit (魏博, headquartered in modern Handan, Hebei). Zhu took over the defense of Tianping's capital Yun Prefecture () after Cao's death and was able to prevent it from falling to Han. Then-reigning Emperor Xizong thereafter made Zhu the acting military governor.