Mansfield Park is one of the most important novels of Jane Austen.People used to analyze the morality which is reflected in this novel from the aspect of the didactic tradition of women novelists.This paper will treat Mansfield Park from a new aspect：moral preaching.Austen used many methods to express moral preaching,such as corroborate repeating,evangelical lexicon,free indirect speech,moral discussion.The application of moral preaching in Mansfield Park brings a boarder space for women novelists to show their talent in the field of writing.