The invention provides a device and method for automatically loading an anti-islanding protection test system. The device comprises a data acquisition unit, a data processing unit and a RLC load adjusting unit, wherein the data acquisition unit, the data processing unit and the RLC load adjusting unit are sequentially connected. The RLC load adjusting unit respectively controls a load switch K1, a network side switch K2 and a combination switching switch of the RLC load adjusting unit through output signals. The corresponding automatic loading method is used for detecting the output power of a photovoltaic system on line and in real time, RLC loads are rapidly, automatically and accurately adjusted, resonance of three-phase independent alternating current electric equipment is generated, and the testing process is convenient to conduct, fast and accurate.