An experiment system of "pulsed light-continuous probe-light-continuous erasure light" is built. By using modulated Q pulse light of 532 nm and continuous probe light of different wavelengths, fast photoresponse characteristic of photocycle and photoabsorption of different intermediate based on bacteriorhodopsin (BR) film are studied. Microsecond optical switch is observed and BR molecule distributing of different intermediate is analyzed when the exciting pulse is over.