The relationship between structures and photocurrent generation properties in a series of dye congeners based on a hemicyanine template has been investigated by using their LB film modified ITO electrodes in a traditional three-electrode cell under the same conditions. Experimental data and semipirical quantum calculation results show that the molecular polarity is the key factor for the quantum yield of photocurrent generation in this kind of molecule. The effect of applied bias voltage, addition of electron donors and accepters, and saturation degree of O-2 or N-2 on photocurrent generation of the selected one has also been examined.