Objective In existing methods for treadmill exercise intensity controlling, the majority of them uses closed-loop system. The designing of control system is complicated, and the cost is high. And the need of the real-time monitoring heart rate increases the complexity of the control. In order to solve the problems of complexity of control system and the high of cost, this paper proposes an open loop control method of exercise prescription intensity based on treadmill, and we verify the accuracy of the control scheme through experiment. Methods First, we obtain the basic physiological information and health and chronic disease questionnaire results of the trainers, and test their cardiopulmonary endurance, then we determine their target heart rate range. Second, according to the linear relationship between the intensity and heart rate, we obtain the control plan of the exercise intensity. Furthermore, we obtain reasonable speed and slope based on the relationship between the exercise intensity and the speed and slope, and the speed and slope of the treadmill are adjusted automatically through the computer program to control the rotation rate of the power motor and the thrust of the lifting motor. Finally, we choose 50 students to wear heart rate measurement equipment to exercise on the treadmill according to the exercise intensity control scheme, and real-time heart rate and target heart rate are recorded. Results The average of the difference in the participants is in the range of -1.915 to 3.113. The standard deviation of the difference is in the range of 2.306 to 4.718. Conclusions When the exercise prescription intensity based on treadmill is provided open control, the real heart rate is in consistent with target heart rate, which provides a simple, scientific, effective and low-cost control method, and it can be applied in daily fitness guidance further.