Abstract: In this paper,numerical investigations on flammability limit of axisymmetric count-flow laminar diffusion flames of CO,CH₄ mixed fuel were conducted by using the detailed kinetic mechanism(GRI-Mech 3.0).The peak flame temperatures of the flames with different mole fractions of CO and strain rates were obtained,and the influence of the variation of α_CO and strain rates on flammability limit was understood.Then the effects of main factors on flame characteristics were studied.It is found that the flame temperature decreases obviously with increasing strain rate.The formation rate of OH is reducing along with the increasing α_CO,which leads to the decrease of the flame temperature,as well as the combustion intensity.