Abstract: Combustion and explosion experiments were carried out in explosion tank of 10 m³ volume with methane-air mixture (9.5% methane). The methods of optical video camera and pressure measurement were adopted to observe the spread process of the flame. The characteristic parameters of the flame were obtained as the flame propagation, The results show that the observed flame could be divided into two stages: the flame stable growth stage and the strenuous burning stage. Depending on the adopted method, the burning velocity of the mixture methane/air is 0.344 m/s and 0.391 m/s, which indicates that the result from each of two methods is coincident basically. The maximum of explosive characteristic index occurs at 0.75 m, while the explosive characteristic index at wall has a bit smaller value.