The invention relates to an outdoor mobile robot photovoltaic automatic charging method. The method comprises a GPS receiver (1), an electronic compass (2), an inertia gyroscope (3), a light intensity sensor (4), a power supply voltage measuring circuit (5), a controller (6), a linear push rod motor (7), a push rod motor-drive circuit (8), a limiting protection circuit (9), a solar energy photovoltaic plate (10), a solar energy charging control circuit (11) and a charging battery (12). When an outdoor mobile robot is at an under-voltage state, a work state can be paused, the outdoor mobile robot is automatically controlled to perform azimuth adjustment, a linear push rod is driven, and the solar energy photovoltaic plate can face sunlight for photovoltaic charging. After the charging is finished, the solar energy photovoltaic plate can be automatically lowered, and the normal operation state of the robot is recovered.