A method and system for detecting an amount of shale oil based on an occurrence state, wherein an occurrence-state-based shale oil quantification model is established in accordance with a kerogen swelled amount, an amount of kerogen absorbed oil, an amount of free oil in an organic pore, an amount of adsorbed oil by an inorganic mineral and an amount of free oil in an inorganic pore, and detects an amount of shale oil is detected in accordance with the occurrence-state-based shale oil quantification model, such that the accuracy of the evaluation of shale oil mobility is improved.