The effect of varying the fuel and oxidizer composition on flame characteristics in a non-premixed oxy-methane flame was experimentally investigated in a lab-scale furnace with a slot-type burner. The fuel composition was varied in the range of X-F,X-CH4 = 70 similar to 100%, X-F,X-H2 = 0 similar to 15%, X-F,X-CO = 0 similar to 10%, and X-F,X-CO2 = 0 similar to 30% while the oxidizer composition was changed in the range of X-Ox,X-O2 = 70 similar to 100 and X-Ox,X-CO2 = 0 similar to 30%. Flow velocity at the nozzle exit was fixed at u(F) = 25 m/s for the fuel jet and u(Ox) = 25 m/s for the oxidizer. The objective of the current study was to investigate the effect of varying the fuel and oxidizer composition on flame stabilization, flame luminescence, flame slope, liftoff height, flame length, and furnace inside temperature in a non-premixed oxy-fuel flame. The addition of H-2 and CO (carbon monoxide) to a fuel jet had the positive effect of broadening the flammable limit. The hydroxide radical chemiluminescence (OH*) intensity was related to adiabatic temperature. The flame slope was affected by global equivalence ratio and the mass flow rate between the fuel and the oxidizer. The liftoff height decreased with the increase in edge flame velocity while the flame length decreased with the increase in the Peclet number of unburned gas. (C) 2014 Elsevier Ltd. All rights reserved.