Abstract: To address sidewall waviness, layer-height fluctuation, and lattice-node closure difficulties caused by heat accumulation during CMT wire arc additive manufacturing of 316L stainless steel thin-walled lattice structures, the effects of process parameters and interlayer temperature control on forming stability were investigated using melt pool imaging, infrared thermography, and three-dimensional laser scanning. Thin-walled lattice structure forming was also verified. The results show that a high wire feed speed enlarges the melt pool and extends the thermal tail, which intensifies interlayer heat accumulation during continuous multilayer deposition and increases sidewall waviness and layer-height fluctuation. Interlayer temperature control at 60℃ reduces the initial temperature before subsequent deposition, weakens thermal cycle accumulation, and improves the geometric stability of thin-walled structures. Furthermore, positioner-assisted posture adjustment combined with segmented spot deposition enables pyramidal lattice strut growth and top-node closure, achieving integrated forming of a 316L stainless steel thin-walled lattice specimen. This study provides a process reference for stable CMT wire arc additive manufacturing of thin-walled lattice structures.