This study was conducted to determine the content validity of the interest assessment instruments and students' interest in physical fitness activities. Researchers will determine the validity and reliability of the Children's Attractive to Physical Activity (CAPA) questionnaire to assess the child's interest in physical fitness activities to ensure the validity of the items (instruments) to be defensible, accurate, appropriate and relevant to the study, and usability and can provide meaningful information. The results of this study show that children's Attraction to Physical Activity questionnaire (CAPA) has a high literacy content value of .78. and the value of the true expertise of the field expert is .77. Therefore, the correlation value of questionnaire reliability was obtained through the Cronbh Alpha method of r = 0.76. This can be explained that the contents of the Children's Attraction to Physical Activity (CAPA) questionnaire are very relevant to use.