‘Learn how to learn’ is the most important educational goal in 21st century.  The information literacy and skills are the key competences for lifelong learning.  The purposes of the study were to design portfolio system of information literacy and to examine the validity of the portfolio.  The framework of the portfolio was based on Big Six skills approach.  The following elements of the portfolio were developed: information tasks integrated into subject area units, scoring procedures for each of the tasks, the structure of the portfolio, and the reliability and validity study of the portfolio.  The distinguishing features of the portfolio are model-based framework, integrated information tasks, and context-sensitive consideration.  Based on information literacy literature review, teacher interview, and curriculum analyses, researcher designed and developed the content of the portfolio, the information tasks, and the rubrics.  Three aspects of validity highlighted by Messick (1995) were used as validity criteria for the portfolio: the convergent and discriminant evidence, the consequential, and the substantive aspects.  Results showed that the portfolio had good convergent validity, but lacked of good discriminant validity.  The portfolio enhances students’ information literacy and has positive influence on teaching.  The big six skills were actually used by students in the information assessment tasks.