Now in the age of electricity, electric motors plays an important role in the industrial and agricultural productions and people's daily life. As the most common type of motor, DC motor contains the advantages of linear with good mechanical properties, a wide speed range, a good start and a simple control circuit . So in all areas of society it's implemented on a comprehensive application. With the development of society, all kinds of intelligent products are found in the home . In order to achieve portability of products, low product and the restrictions on the power supply, small DC motor applications have a wide range. To change the DC motor speed regulation, there are a variety of ways,.This article introduces PWM DC motor adjustment and realization based on SCM software, to provide a PWM speed control method. This article describes the implementation based on single chip with a PWM DC motor which adjust the basic methods, knowledge of DC motor speed regulation, and PWM adjustment of the basic principles and implementation methods. The article Highlights MCS-51 microcontroller generated PWM signal by software means and introduces a unique method by using counting methods realization of additional software PWM signal duty cycle delay adjustment method. This kind of method provides an effective way For DC Motor Speed Control System.