In this study, the waste gasification gas was co-fired with LNG and water electrolysis gas (or stoichiometrically well-mixed hydrogen oxygen gas) in order to see the change of flame characteristics compared to the standard case of wellknown LNG flame. In detail, a numerical study was made to figure out the fundamental combustion characteristics ofthe waste produced gas blended LNG or hydrogen-oxygen mixture gas flame in an existing industrial LNG combustor.As a preliminary study, the mixture of 70% synthetic gas blended with 30% LNG or hydrogen-oxygen mixture gas wascompared with pure LNG fuel with maintaining the same total input of heating value. Especially, the reason to includethe hydrogen-oxygen mixture gas, that is, the mixture of H2 and 1/2 O2, as a fuel is following:the hydrogen-oxygenmixture gas has a rather high heating value since it does not need air as oxidizer, which consists of 79% N2 as inertmaterial. The result shows that the case of mixture fuel with LNG exhibits more broadening flame shape than the 100%LNG flame. Further, it is observed that there is a phenomenon like a disappearance of CTRZ (Central ToroidalRecirculation Zone) and flame extinction showing partial lift-off of flame around strong swirl flow near burner. This kindof observation appeared in the case of blended fuel mixture is considered probably due to the increased effect of velocityand turbulence stress caused by the mass increase by the addition of low calorific fuel. However, the case of mixturefuel with hydrogen-oxygen mixture gas and water vapor does not show any flame instability phenomenon due to increasedflow rate as in LNG case.