The flame surface density for turbulent premixed combustion on a nozzle-type burner is measured by planar laser-induced fluorescence (PLIF) and image processing techniques. The maximum flame surface density tends to show linear dependence on the K-factor given as a function of the integral length scale and u(0)'/S-L. The flame surface density shows an asymmetric profile in (c) over bar space with the peak location correlated in terms of the dimensionless parameter, N-B, which represents the degree of gradient or countergradient diffusion by turbulence. At values of N-B close to unity the peak occurs at a value of (c) over bar of about 0.7. As N-B increases above unity, the peak moves to a lower value in (c) over bar space, approaching a symmetric profile. The thickness of a turbulent flame brush nondimensionalized by the integral length scale tends to show linear dependence on the H-factor which is obtained by integrating the first moment equation of the reaction progress variable. The flame surface density increases at a higher ambient pressure due to decrease in the laminar burning velocity and the length scales of flame wrinkling.