Leo IX started the papal reform in the eleventh century, which made great influence in the history of the Roman Catholic Church and even the whole western world. Leo IX was different from his predecessors, as he was the first pope from Deutschland and he lived in a monastery in his early life. This paper studies Leo IX's early life and would help to understand the origin of his reform, and it is found that Leo IX was deeply influenced by his monastic early life, and this work would help study the papal reform in the eleventh century.