Valve bonnet and valve seat are the main factors that compose the metering error of gas meter. For evaluating the tightness of gas meter valve in a quantitative way, laser displacement sensor based on triangulation was applied to scan surface profile of the valve working face which was on the two-dimensional air floating stage. And then, surface roughness parameters were calculated through a Gaussian filter, which could judge the tightness of gas meter valve qualified or not. The results indicate that surface roughness has a big difference between the qualified and unqualified workpiece. Besides, there is a little deviation between the experimental value and the roughmeter measuring value, which has no impact on the testing result. The tightness of gas meter valve can be judged by measuring the valve surface profile, which provides a scientific basis for evaluating the quality of gas meter valve in a quantitative way.