Abstract: Considering the characteristics of through-the-wire sensor, a real-time tracing and control system of torch height for waveform-controlled short-circuit CO₂ welding is established based on the MCU (Motorola MC6SHC11Al) in this paper. After real-time measuring and processing the wire extension signal during the period of short-circuit,the real-time and precision control of torch-height for short-circuit CO₂ welding is realized by using this system designed with reasonable framework. The experimental results show that the system has excellent stability and dynamic response under different conditions,such as different slope angles, wire feeding rates and welding speeds. This realization makes the welding process more stable and the welding quality improved.