The functional organic monolayer/n-Si(111) assembly was fabricated for an investigation of photoelectric memory effect by the Langmuir-Blodgett technique from 1-(2-carboxyethyl)-4-[4’-N,N-(dioctadecylamino)stryl] pyridium (P-I). The measurement of the surface photovoltage spectra (SPS) of this assembly shows that it has an erasable photoelectric memory effect : after a voltage of 20 V was applied to this assembly upon irradiation with visible light, the surface photovoltage (SPV) of this assembly becomes stronger, the increase of SPV can remain; followed by the application of a voltage of -20 V in the dark the SPV can return to the initial value (i.e. the value without being treated with an external field). Based on the principle of surface photovoltage spectroscopy, it is suggested that the electron acceptor 2-carboxyethyl pyridium in the hydrophilic head of P-I can capture the photogenerated electron from the conduction band of n-Si(lll) as an electron trap upon irradiation with visible light under the help of a positive external electric field, and the trapped electron can return to the conduction band of n-Si(111) on the application of a negative external electric field.