This paper analyzes the status quo of the connotation research of expert-type principals and conducts mathematical and statistical analysis in the form of the questionnaire to obtain the expert-content characteristics of the principals.

Middle school principal training during the Eleventh Five-Year Plan is being carried out on the condition of value orientation rationalization,the enlargement of school autonomy rights,principal professionalization,the marketization of training and the refinization of traning.

Based on reviewing the development stages of the principal professionalization and their implicit knowledge, this paper aims to analyze what the structure of the principals professional knowledge is and how their implicit knowledge is changed into explicit knowledge.