Since high-mobility electron gas, which is also called two-dimensional electron gas, was discovered at the LaAlO₃/SrTiO₃ (LAO/STO) interface, SrTiO₃-based heterostructures and nanostructures have become an attractive platform for novel nanoelectronic devices. Exploring the novel physical properties of LAO/STO interface and the mechanisms of interface effect is the key to designing and fabricating the new photoelectric devices. The LAO/STO sample is prepared on an STO (001) substrate by pulsed laser deposition. In order to study the influence of interface effect on photovoltaic effect in the LAO/STO sample, a KrF pulse laser with a wavelength of 248 nm and an energy density of 50 mJ/cm² is chosen as an ultraviolet light source, a sampling oscilloscope of 350 MHz is used to measure the photovoltages, and a precision adjustable slit is adopted to control the size of irradiation area. The photovoltaic effect is studied under the condition of applied electric field at ambient temperature. The experimental results prove that the photovolatge of irradiating on the side of sample (LAO/STO interface) is higher than on the front of sample (film surface) under the same area of irradiation. Lateral photovoltaic effect is discovered in the LAO/STO sample. Irradiating on the side of sample (LAO/STO interface) can further improve the lateral photovoltaic effect in the LAO/STO sample. The open-circuit photovoltage depends linearly on the illuminated position, and the sensitivity reaches 36.8 mV/mm. The sensitivity of the lateral photovoltaic effect can be modified by the bias voltage. The experimental results not only contributes to better understanding the interface effect in LAO/STO interface, but also provides a basis for designing and using photoelectric devices for position-sensitive detection.