The invention discloses an oil-soluble temporary plugging agent and a preparation method therefor and solves the technical problem of leakage of a workover fluid in a workover process of high temperature leakage oil and gas reservoirs. The oil-soluble temporary plugging agent is composed of the following components in parts by weight: 0.5-2 parts of C5 petroleum resin, 0.5-2 parts of modified petroleum resin, 0.1-0.5 part of rosin modified phenolic resin, 0.4-0.6 part of xanthan gum, 2-5 parts of potassium chloride and the balance of water, wherein the softening point of the C5 petroleum resin is greater than or equal to 140 DEG C and the softening point of the modified petroleum resin is greater than or equal to 145 DEG C. External fluids in shafts of oil and gas wells 3500 meters or over 3500 meters can be prevented from invading to pollute the oil layer.