The invention discloses a swelling preventing and degumming agent for bio-based methanol gasoline and a preparation method of the swelling preventing and degumming agent. The swelling preventing and degumming agent consists of the following ingredients in percentage by volume: 40-50% of plastic corrosion preventing ingredient, 25-30% of swelling preventing and anti-aging ingredient and 25-30% of degumming preventing ingredient; and the swelling preventing and degumming agent product is prepared through uniformly stirring the three functional ingredients at normal temperature. According to the swelling preventing and degumming agent and the preparation method of the swelling preventing and degumming agent, cleanable, environmental-friendly, reproducible and degradable petroleum yeast fatty acid soap is selected as the main raw material of a cheap additive, so that the energy is saved and the emission is reduced; and compared with the prior art, the swelling preventing and degumming agent is low in cost, non-toxic, free of pollution, low in dosage and remarkable in swelling preventing and degumming effect and cannot cause secondary pollution to the environment. According to the swelling preventing and degumming agent and the preparation method of the swelling preventing and degumming agent, the phenomenon that rubber, plastics and fiber gaskets of a fuel system are corroded, swelled, stuck, embrittled and softened due to use of methanol gasoline in the prior art is overcome; and the swelling preventing and degumming agent has the advantages that the preparation is simple, the raw materials are easily available, automotive component materials are not required to be transformed and modified, the swelling preventing and degumming effects are good, and the degumming capacity is strong.