The paper introduces the algorithms of dynamic sliding mode control and applies this way into speed control of alternating current servo system. Comparing with traditional variable structure control method, we could find the chattering produced by variable structure control is greatly alleviated. The theoretical analysis and simulated results show that dynamic integral sliding mode control can eliminate the chattering of system basically, furthermore, it can let system respond quickly and have not static. When the load changed suddenly, the system only produces tiny dithering and the resuming time is very short. These phenomena show that it has better adaptability