The high speed cameral and schlieren images methods were used to record the photograph of flame propagation process. Meanwhile, the ionization current probes were set up to detect the reaction intensity of the reaction zone. The characteristics of methane/air flame propagation and microstructure were analyzed in detail by the experi-mental results coupled with chemical reaction thermodynamics. The high speed schlieren image showed the transition from laminar flame to turbulence combustion. The ion current curves disclosed the reaction intensity and combustion characteristic of flame front. In the test, the particular tulip flame was formed clearly, which was induced to some extent by turbulent combustion. Based on the schlieren images and iron current result, it can be drawn that the small scale turbulence combustion also appears in laminar flame, which thickens the flame front, but makes little influence on the flame front shape. During the laminar-turbulent transition, the explosion pressure plays an important role on the flame structure change.