Online instantaneous two-dimensional imaging of reaction zone and different intermediate species in flames are important and fundamental in the research of turbulence combustion. In methane/air premixed flames, the instantaneous imaging of flame reaction zone is achieved using laser photodissociation-induced fluorescence technique with the 5th harmonic (2128 nm) of an Nd∶YAG laser as excitation source.The online instantaneous imaging of CH3 radicals was accomplished for the first time with this technique. The advantage of this technique was analyzed over other typical PLIF techniques in terms of visualization of flame reaction zone. The influences of other combustion intermediates and flame equivalence ratio to the single-shot imagining of CH3 were studied, and the application range of the technique was also discussed. The result shows that single shot imaging of reaction zones in our measurement with a signal-to-noise ratio (SNR) of 8. Single shot imaging of CH3 has better SNR by LPIF in premixed methane/air flames with the equivalence ratio from 10 to 14, or when the concentration of CH3 is higher than 9×1015 molecules·cm-3. The results provide very important information for the application of this technology in power machinery and other field.