n-dodecane steam reforming (SR) process was investigated from both experimental and modelling views in gliding arc plasma. The effects of water-carbon molar ratio, n-dodecane concentration, input power and residence time on the conversion, yield and energy efficiency EE(C12H26) and hydrogen energy yield EY(H2) were revealed. The most dominant spectral lines detected by optical emission spectroscopy (OES) are CN violet and Hα (3d2D-2p2p0). The highest yields of H2 and CO are 50.1% and 49.9%, respectively. A zero-dimension reaction kinetic model containing 105 species and 793 reactions was developed for the SR process. Using CHENKIN-PRO, the presumable reaction pathways of n-dodecane, H2, CO, H2O and CO2 were described in detail. H2 and CO were produced mainly through reaction C2H4+H⇌C2H3+H2 and reaction HCCO+H⇌CH2(S)+CO.