The purpose of this study was to identify the effects of portfolio assessment instruction system on physical education teaching-learning in high school by ethnographic approach. This study focuses on the efficiency of integration of teaching-assessment, the efficiency of achievement of learning goal and the effectiveness of student-centered instruction. This study was compared out of two classes of the first-year students in S High School of Uijeongbu City in which one class hired portfolio assessment and the other applied traditional assessment. Data collection was made by employing participant observation, narrative observation, in-depth interview and descriptive survey. The Data collected were analyzed by using taxonomic analysis, causal chain analysis, process analysis, frequency analysis and learning time analysis. As the result of the interview with students and the analysis of descriptive survey, students thought portfolio assessment instruction was a proper method and was helpful in achieving learning goal. Consequently portfolio assessment instruction was very effective in integrating teaching and assessment. Learning achievement result in cognitive domain also revealed higher than traditional assessment groups. Portfolio assessment instruction was very helpful in improving the goals in affective domain with the help of the interaction among students, the interaction between students and teachers and self-evaluation process.