This paper has a purpose to improve problems we've had so far in evaluating for special activities and realize a desirable evaluation in special activities by applying performance assessment, which rises as alternative plan, to special activities. To elevate the completeness of this study, I examined the meaning, changes and evaluation of special activities, and also did literature study on the theoretical background and characteristics of evaluation in music subject and performance assessment Based on the contents studied above, an evaluating plan and paper of orchestral music class among which well reflect the features of performance assessment as well as groping for the justification and principles of performance assessment in orchestral music class is suggested focusing on an orchestral work. As written above, applying performance assessment to special activities is expected to have the following effects. First, by evaluating not only the result and also the process of activity, we can give immediate feedback to students. Second, by evaluating not just achievement level but also each individual's various features, we can give meaningful information to students. Third, doing self-evaluation by students besides that of teacher, we can raise students' correct self-evaluation, spontaneity to class and creativity. Fourth, through fellow evaluation and group evaluation, we can make students have correct understanding of their friends, consideration and concession. Fifth, through various evaluation ways, we can derive desirable attitude and value view forming form students. For the essential pursuit of special activities and true school education, we should keep studying performance assessment.