The invention relates to a blocking anti-collapse agent for drilling fluid on the basis of oil-containing mud and a preparation method thereof. According to the technical scheme, the blocking anti-collapse agent is prepared form, by weight, 30-80 parts of oil-containing mud, 30-80 parts of petroleum asphalt, 30-160 parts of a sulfonating agent, 10-200 parts of a sodium hydroxide solution, 30-300 parts of a light organic solvent, 1-20 parts of surfactant, 1-30 parts of filtrate reducer and 1-30 parts of an inert filling material. The blocking anti-collapse agent has the advantages that the blocking anti-collapse agent can be used in water-based drilling fluid, can well reduce the filter loss and inhibit shale hydration expansion, and can well lubricate a drill bit. In the preparation process, the oil-containing mud is fully used, no harmful matter is discharged, a new means is provided for treatment and utilization of the oil-containing mud of an oil field, and the treatment and utilization rate of the oil-containing mud of the oil field is increased. The blocking anti-collapse agent can relieve the pressure that a large amount of oil-containing mud of the oil field is difficult to treat, and a cheaper raw material is provided for the blocking anti-collapse agent for the drilling fluid.