The invention relates to an automatic optical detection method and an automatic optical detection system. The method comprises the following steps: obtaining liquid crystal screen images in preset display states of multiple pure colours, grey-scale images, grey-level images and multi-colour alternating images respectively; processing the liquid crystal screen images in the obtained display states, judging whether a liquid crystal screen has defects or not, if so, then identifying the types of the defects, recording the positions of the defects, and counting the number of the defects; obtaining the liquid crystal screen images of the turned-off liquid crystal screen in an external light irradiation state; processing the liquid crystal screen images in the obtained external light irradiation state, and judging whether the liquid crystal screen has appearance defects or not. According to the automatic optical detection method and the automatic optical detection system provided by the invention, brightness, dark spots, bright lines, dark lines, surface defects and appearance defects can be detected, defect detection types are increased, unqualified products are reduced, the quality of the liquid crystal screen is improved, a production line can be improved, and the production yield of the liquid crystal screen can be increased.