Measurements of laminar burning velocities and Markstein lengths of n-butanol-air premixed mixtures was made over a wide range of equivalence ratios at initial temperatures of 413, 443, and 473 K and initial pressures of 0.1 and 0.25 MPa using the high-speed schlieren photography and outwardly propagating flame. Effects of laminar flame thickness, thermal expansion ratio, and flame Lewis number on flame stability response were studied. Schlieren photos of flame propagation are recorded. The results show that laminar burning velocities of n-butanol-air premixed mixtures are increased with the increase of initial temperature, and they decrease with the increase of initial pressure. Markstein lengths are decreased with the increase of the equivalence ratio, and they decrease with the increase of initial temperature, and all these indicate that the flame instability is increased with the increase of equivalence ratio, the decrease of initial pressure, and the increase of initial temperature.