Laser ignition technology has received widespread attention in aerospace power systems due to its flexible positioning, high energy density, and fast heat release rate. It mainly relies on the aerodynamic, thermal, and chemical effects of plasma. This article is based on laser ignition experiments conducted in a constant volume combustion chamber of methane/air mixture. The focus is on studying the flame propagation characteristics of single pulse laser-induced ignition, analyzing the influence of laser pulse energy on ignition and flame propagation characteristics, and conducting numerical simulation studies to evaluate the influence of plasma chemical effects. Research has found that the initial flame nucleus exhibits a “three lobed structure”, which is very similar to the vortex ring structure formed by laser-induced air breakdown, verifying the important role of plasma aerodynamic effects in ignition and thermonuclear development. Further comparative analysis was conducted on the development characteristics of ignition flame nuclei with and without chemical effects. The results showed that compared to the aerodynamic and thermal effects of plasma, chemical effects had little effect on the development of flame nuclei.