The present article systematically investigates the laminar explosion behaviors of syngas with wider ranges of fuel concentrations (0.4 3.0 in equivalence ratio) and composition fractions (30%similar to 70% in volume fraction ratio of H-2 in syngas) in a 28.73-L spherical vessel. The temporal traces of explosion overpressure and the variations of four essential explosion indices (maximum explosion pressure, explosion duration, peak pressure rise rate, and deflagration index) have been studied, the influencing factors and mechanism have been analyzed and discussed. The influences mechanism of composition and concentration on maximum explosion pressure are discussed from the viewpoint of heat loss to the vessel wall. The correlation of explosion duration to laminar burning velocity has also been discussed, the result indicates that the correlation is mainly determined by fuel composition when the burning velocity beyond certain level. The critical equivalence ratio for peak pressure rise rate in syngas explosion is determined by the maximum pressure for H-2-enriched syngas but it is determined by explosion duration for CO-enriched syngas. Furthermore, the safety issues about syngas are also discussed upon deflagration index.