Based on the purpose of constructing a general model of principals' competences, this article presents a review of the literature in the past ten years, including eight dissertations and six articles, with a sample of 2998 principals and 224 items of competences. Through a meta-analysis, we construct a general model of principals' competency involving nine items of competences. Frequency analysis shows that among all the competencies, leadership is the most important competence, the second in importance are training others and creativity; the third are self-control and interpersonal sensitivity, and the fourth are problem analysis, influence, relationship building and communication. On the one hand, the findings of this study integrate the relatively scattered outcomes about principals' competency research; on the other hand, they can provide empirical evidence for standardized competency training for principals in primary and secondary schools.