Good rectifying current-voltage characteristics and nanosecond photoelectric effects are observed in the p-n heterojunctions of La0.gSr0.1MnO3/SrNb0.01 Ti0.99O3 fabricated by laser molecular beam epitaxy. The rise time is about 26ns and the full width at half maximum is about 125ns for the open-circuit photovoltaic pulses when the La0.gSr0.1MnOs film in the heterojunction is irradiated by a laser operated at wavelength 308nm with pulse duration of about 25 ns. A qualitative explanation is presented, based on an analysis of the photoelectric effect of p-n hetero junction.