Abstract: Various amounts of a liquid crystal such as 4-methoxybenzylidene-4'-n-butylaniline (MBBA) were added respectively into chlorophyll a (Chla)-isooctane solutions of the same concentration. These solutions were coated respectively on to platinum plates to form liquid crystal-chlorophyll platinum electrodes for determining the different photo-induced potential ΔE. On the other hand, these solutions were coated respectively on to glass plates to form the glass plates with the liquid crystal-chlorophyll layer for determining the different height of 743 nm characteristic peak of derivative spectrum h/h_T. It was found that both of ΔE and h/h_T apear the maximum values with the increase in quantity of MBBA. The same result can be found by substituting iso-octane by the petroleum ether and the isooctane-petroleum ether (1:9V/V). The MBBA molar concentration range in which all of the six maximum values from above three solvent systems occur is 0.001±0.0005. The regularity of the experimental results was theoretically elucidated by the principle of derivative spectrum, the molecular structure and the characteristics of liquid crystal.