The objectives of this study were to look into the requirements of exercise instructors' professional competency, and to compare furthermore the recognition differences of exercise instructors' different background toward their professional competency. The study based on the interviews conducted with a custom-designed questionnaire titled “Requirements of Exercise Instructors' Professional Competency.” The subjects of this study were exercise instructors from 61 Taipei Health and Fitness Clubs. The total of 300 questionnaires were handed out, and the rate of valid replies was 66.9%. The methods applied to the analysis were description statistic, T-test and single variable analysis, and Scheffe method was analysized for comparison. Conclusions were drawn as follows: 1.Exercise instructors showed remarkable knowledge on all aspects of significance extent of professional competency. “Instructional operations” had the highest average value. Six professional proficiency categories in this study are in the order of “instructional operations”, “interaction”, “administrative management”, “work attitude”, “relevant knowledge”, and “data processing”. 2.Exercise instructors' knowledge on the requirements of professional competency does not vary with sex, ages, work years, highest education background, fields, and professional certifications. 3.Among different job categories, physical fitness trainers apparently have more requirements for “instructional operations” than aerobic trainers, and more for “instructional operations” and “data processing” than swimming coaches. Trainers in other categories require much more “instructional operations” and “data processing” than aerobic trainers, and need to strengthen their professional competency in “data processing” than swimming coaches.