Multi-wire sawing is a novel method for slicing silicon. The tension control of wire is a vital factor that has impaction on the slicing process. Along with the modern wind machine developing to higher speed and precision, tension control technology becomes more important. This paper introduces a closed-loop tension control system with the digital signal processor (DSP) with function modules as its control kernel, the alternating current (AC) servo motor as execute element and the radius-following device to accomplish the real-time radius compensation. The mechanism of the tension control system is analyzed and the numerical model is set up. The compensation technique of the radius of the scroll is analyzed. Experimental results show that the system is well qualified with high control precision and high reaction speed.