The purpose of this study was to examine the effects of moderate acute exercise on RPE and affects among different objective and subjective fitness level. Subjects are 35 healthy female college students (mean age =19.8 ± 1.3years,height=160.6 ± 6.2 cm, weight=55.8 ± 7.1 kg, BMI=21.6 ± 2.6) who participated in this study voluntarily. Based on subjects' areobic exercise capacity and perceived ability, subjects were categorized as four groups (high aerobic capacity/high perceived ability, high aerobic capacity/low perceived ability, low aerobic capacity/high perceived ability, low aerobic capacity/low perceived ability). All subjects' mean estimated VO �� max is 34.7 ± 10.2ml/kg/min. During the experiment, subjects were asked to ride the computerized cycle ergometer in 75% HR max (220-age) intensity at 60 rpm for 20 minutes. In order to keep the subjects' pulse rate in the target. Subjects' work load were increased or decreased 0.1 kg/m when their heart rate deviated b3 bpm from the target pulse rate, Subjects' RPE at 5th, 10th 15th, and 20th minute, affects before and after exercise were recorded during the exercise. The results of this study indicated that： (1)There was no significant difference of aerobic capacity and perceived ability on RPE in the moderate acute exercise. (2) There was a significant benefit in positive and negative affects after 20 minute exercise. (3)There was a significant main effect of aerobic capacity on positive affects in the moderate acute exercise. High aerobic capacity subjects experienced greater positive affects than low aerobic capacity subjects after 20 minute exercise. (4) There was no significant difference of aerobic capacity and perceived ability on negative affects in the moderate acute exercise.