Optically induced annealing technology has provided promising strategies to synthesize graphene for future flexible electronics. Focused laser-assisted methods have the capability of direct graphene growth, but have significant drawbacks such as small beam size, and locally different intrinsic properties caused by energy variations of each pulsed shot. Herein, a novel synthesis method of multilayer graphene (MLG) via xenon flash lamp with intense and achromatic light is presented. An extremely high temperature (over 1500 degrees C) by a single flash irradiation induces the MLG with about 15 layers in milliseconds time scale. Experimental and theoretical studies reveal characteristics of the MLG with I-2D/I-G of 0.65 and average sheet resistance of 3.272 x 10(3) sq(-1) as well as photothermal interactions between flash and metal catalyst. The synthesized MLG is successfully transferred onto plastic substrates, demonstrating a new feasibility of the flash lamp system for next-generation flexible electronics.