The invention discloses an on-site disposal method for oil base drilling cuttings and belongs to the technical field of chemical industry environmental protection. According to the on-site disposal method, after being ground, pressurized and preheated, the oil base drilling cuttings are mixed with water and an oxidant, and the mixture enters a reactor; the efficient cleaning characteristic of supercritical water oxidation is used, and organic matter in the oil base drilling cuttings is oxidized and degraded into water, carbon dioxide and other inorganic matter thoroughly; solid products and gas and liquid products obtained after reaction are separated in the reactor and are discharged from an upper discharge outlet and a lower discharge outlet correspondingly; and the discharged products can be directly discharged into the environment or can be subjected to resource utilization as needed. Movable compact equipment developed based on the on-site disposal method can be transported to a drilling site as needed, on-site disposal of various oil-gas field oil base drilling cuttings is achieved, and environmental harm of the oil base drilling cuttings is eliminated from the source.