The combustion characteristics of premixed laminar flames of natural gas with high methane content were studied to reveal the influences of dilution ratio and diluent kinds(N

2

and CO

2

)on the combustion characteristics such as the laminar flame speed

NO

x

mole fraction

combustion pressure and combustion duration. The study results show that the laminar flame speed

the mass burning flux and the heat release rate all decrease with the increasing of dilution ratio; and with the addition of diluents

the flame temperature decreases

hence decreasing the NO

x

mole fraction. The Markstein length and flame thickness also increase with

the dilution ratio

indicating that the flow instability of flame is suppressed. The combustion pressure peak and the pressure rising rate decrease while the combustion duration increases with the addition of diluents. Additionally

compared with N

2

CO

2

has more obvious dilution effect on the combustion characteristics of natural gas with high methane content.