Abstract: The paper introduces a method for real-time detecting broken filaments in the process of winding viscose filaments.By illuminating viscose filaments,the broken-filaments will become an enlarged image on the sensitive surface of the photo electricity sensor,and the image will weaken the luminous flux of photoelectric cell,by monitoring the signal,the system can detect and count broken filaments.Based on this concept,designed a kind of device for detecting broken filaments for viscose filaments based on the circuit detecting principle.It used single chip process 89C51 as the host and accomplish broken filaments detection and counting by the circuits of signal processing,counting,power governing,displaying,and implementing and driving.It has been proven by practical running that the device is characterized by reliable and stable operation,compactness and low cost.