A study of the relation between instantaneous optical absorption and photovoltage in bacteriorhodopsin in room temperature by dye pulse laser with different wavelengthes indicates that: the photovoltage and optical absorption of the BR are not necessarily correlated, besides the amount of optical absorption there are other factors influcing photovoltaic conversion; and the photovoltage of BR at 617 nm is greater than that at 597 nm and 577 nm.