Measurements of Excitation-Emission Matrix (EEM) of polycyclic aromatic hydrocarbons (PAHs) in an atomospheric diffusion burner flame were conducted using a multi-wavelength excitation laser in order to demonstrate the potential of the EEM fluorometry for investigation of soot formation processes in flames. The PAHs in the flame were excited by a coherent multi-wavelength "rainbow" laser light generated by converting the 3rd harmonic (355nm) of a pulsed Nd : YAG laser using a Raman cell frequency converter filled with hydrogen (0.6MPa). The fluorescence from the PAHs excited by different wavelengths in the flame was simultaneously captured using a spectrometer and an ICCD camera as EEM images.