Green conversion of bio-waste rapeseed oil into carbon nanomaterials and syngas is first investigated using atmospheric rotating gliding arc (RGA) plasma. Syngas is the main gas product. The maximum selectivity towards syngas is 65.2% at oil flow rate of 3.5 mL min(-1), while a highest oil conversion rate of 34.7% is achieved at an oil flow rate of 1 mL min(-1). The morphology, order degree, chemical composition, and wettability of carbon nanomaterials derived from waste oil is comprehensively characterized.