Disclosed is an automatic descaling system for high-pressure reactor of laterite nickel ore used in laterite nickel ore processing. The system comprises a high-pressure reactor, multiple mixing devices, multiple detection devices, and a scale removal assembly; the high-pressure reactor is equipped with a feed end and a discharge end at its two ends; within the high-pressure reactor, multiple partition plates are arranged sequentially along the material flow direction, dividing the internal cavity of the reactor into multiple compartments, with any two adjacent compartments being interconnected. Multiple mixing devices are correspondingly installed within multiple compartments; and multiple detection devices are correspondingly installed in the multiple compartments as well. The scale removal assembly comprises an acid storage tank, multiple first connecting pipes, and multiple first control valves. The multiple first connecting pipes are connected correspondingly to the multiple compartments, and each first connecting pipe is connected to the acid storage tank. The multiple first control valves are correspondingly installed on the multiple first connecting pipes. This disclosure finely adjusts the amount of acid injected based on the thickness of the scale, not only achieving a better descaling effect but also correspondingly reducing the usage of acid, thereby lowering the production costs for enterprises.