In Indonesia, more than 26 thousand tons of polyethylene (PE) packaging plastic bags are disposed of into the environment per day. Nanocarbon technology is one solution. Flame synthesis reactor is a method for nanocarbon production. Flame synthesis using argon as a carrier gas and oxygen gas as co-feed gas to produce carbon monoxide (CO) as a source of precursors for the growth of nanocarbon. Oxygen as a co-feed were injected in this reactor for increasing CO. Stainless steel (SS304) is used as a substrate of catalytic media at a temperature of 800°C for 1 hour. Nanocarbon characterized by FTIR, TEM, and XRD. The result of the optimum conditions in pyrolisis of plastic bag waste was obtained at a temperature of 450°C in 10 minutes. The perfomance of flame synthesis reactor showed that carbon nanotubes, onion holow core, quasi-spherical are dominated of nanocarbon with 30% yield. This shows that the flame synthesis reactor is capable for producing CNT nanocarbon based on PE plastic bag waste.