In order to study the laminar combustion characteristics of ethanol, the flame propagation rules of hydrogen and ethanol mixed gas in a constant combustion bomb at different initial temperatures (370 K and 450 K) and equivalence ratios (0.7-1.4) under the conditions of 0.3 MPa initial pressure and 50% hydrogen mixing ratio were researched. The laminar combustion velocity and Markstein length of mixed gas were calculated and the influence of stretching rate on flame propagation velocity was analyzed. The research results were further compared with the literature data and the reliability of calculation model was verified. The results indicate that the laminar combustion velocity of mixed gas increases with the increase of initial temperature. Moreover, the increase of equivalence ratio will increase the laminar combustion velocity of mixed gas, which reaches the peak at an equivalence ratio of 1.2 and then begins to decrease. However, the increase of initial temperature will lead to flame instability under certain conditions. At the initial temperature of 370 K, the Markstein length is always greater than zero and the flame remains in a stable state. The Markstein length is less than zero at the initial temperature of 450 K and the equivalence ratio of 0.7-0.9 and the flame appears unstable state. The higher initial temperature will produce strong convection and turbulence effects, which will disturb the boundary layer of flame and finally cause flame instability. The Markstein lengths at different initial temperatures increase with the increase of equivalence ratio and the stability of flame continuously improves. The data fitting was performed for the calculated laminar combustion velocity and the relationship equation for calculating the laminar combustion velocity of ethanol-hydrogen-air mixture was obtained.