The interaction between Elsinochrome A (EA) and myoglobin (Mb) was investigated using UV-Vis and fluorescence spectroscopy. The results suggested that there was a strong interaction between EA and Mb. In the dark, the interaction occurred on the surfaces amidic acid of Mb, but when illuminated, the interactions happened both on amidic acid and the interior structure of hemachrome of Mb. According to the values of the quenching constant, the thermodynamics parameters, the binding constants and the binding sites, it was showed that the binding interaction of EA and Mb was mainly hydrophobic in nature and the quenching mechanism was static quenching procedure. The change in the micro-circumstance of aminos of myoglobin was studied by synchronous fluorescence spectroscopy.