This study is to examine the basic structure of the professional development of school librarians and to analyze the national evaluation standards, and the states' evaluation tools and self-assessment tool currently used in the United States. The result is as follows: the structure of the school librarians' professional development processes, such as curriculum, certificate, and evaluation, have been affected by the national school library standards published by AASL. NBPTS's Library Media Standards and AASL's Learning4Life evaluation system are proposed as the representative national standards. Many states have developed their standards and tools to evaluate school librarians' performance, these standards are related to the national standards. AASL published A 21st-Century Approach to School Librarian Evaluation for school librarians' self-assessment in 2012, this workbook shows a specific way of developing their expertise.