This study is intended to the effect of the Continuous Running Time Difference on Cardiorespiratory Endurance in order to present effective data for developing middle school students` cardiorespiratory endurance. They took part in this experiment. They are sound physically and spiritually and do not exercise regularly. They were trained with the same aerobic intensity three times a week. They were randomly sampled into 4 groups which consist of 6. According to the continuous running time, they were divided into 4 groups-G Ⅰ (continuous running time is 3 minutes), GⅡ (6 min.), GⅢ(9 min.), GⅣ(comparative group)-and had been trained for 8 weeks. Before and after the training, they performed maximal treadmill work. The results were as the following; 1. VO_2max/kg According to the Running time, There was meaningful between GⅢ and GⅣ. In the efficiency GⅢ was ranked the highest and , GI and GⅣ in order. 2. Ventilation Equivalent There was meaningful between GⅣ, GⅢ, and GⅡ in the Rurnning time. In the efficiency GⅢ was ranked the highest and GⅡ, GⅠ and GⅣ in order. 3. The improvement of anaerobic ventilation threshold effect There was no meaningful for the improvement of anaerobic ventilation threshold effect. According to the above results, The result was necessary for us to study intensity, frequency, duration, types, and time in training per day, so that we may find out practical training methods to improve cardiorespiratory endurance. It is necessary to study a recovery rate after the training and muscular fatigue too. Especially the study about recovery rate will be efficiently useful in planing lessons of school. It is required to study the case of female students in order to find out the gender difference of cardiorespiratory endurance.