The effects of bomb under equivalence ratios, initial pressures and CH4 concentrations on the premixed laminar flames propagation velocity and the laminar burning velocity of coal bed methane-air mixtures were studied in a constant volume combustion bomb by high speed video camera. The results showed as follows, when equivalence ratio is 1.1, laminar burning velocity has the largest value; in initial combustion stage, with the increase of initial pressure, maximum combustion pressure markedly increases, laminar flame spread velocity and laminar burning velocity decrease, and when the flame radius exceeds 40mm, laminar flame spread velocity and laminar burning velocity increase; with the increase of CH4 concentration, laminar burning velocity and maximum combustion pressure increase.