Wire arc additive manufacturing (WAAM) has the potential to become a method to production large and complex metal components, but there is a lot of material waste and energy consumption in the forming of thin-walled metal parts with variable-size. To solve this problem, this paper proposes a method for forming thin-walled parts with variable width and height is proposed, where metal samples are prepared by Variable Polarity (VP) TIG & Fused-deposition Additive Manufacturing (FDAM). This method adopts multi node subsection control strategy. Under the real-time acquisition system of composite dual-vision sensors, through the on-line control of deposition layer size is realized by matching each piece with different process parameters of thin-walled parts. The thin-wall parts with controllable range of 5.5–10 mm and the heights controllable range of 6.5–13 mm. The results show that the multi-node piecewise strategy achieves a stable and convergent control. Compared to the conventional method, the material utilization increases by 51.4%. With a 128% shortening of producing time. The proposed control method can remarkably reduce the frequencies of arc initiation and extinction, improve the production efficiency, and save materials and energy.