Measurements of wall heat flux and ionization current for the case of cold wall and unburned gas temperature 850K were carried out with a stoichiometric methane-air mixture in a head-on quenching regime in a pressure range of 0.8-16MPa. It was found that maximum wall heat flux density increases as P0.5 while the dimensionless maximum wall heat flux (maximum wall heat flux normalized to the rate of energy release in flame) slightly decreases with a pressure rise. The authors evaluated quenching distance independently from the maximum wall heat flux and from the electrical probe current. In both cases the thermal flame quenching model and simplified model of combustion plasma-probe interaction was applied. The accuracy of the ionization probe's method was improved taking into account the influence of pressure and temperature effects on the electrical conductivity of flame. A good correlation between results obtained with two methods was found in all range of pressure.