The application discloses a plastic coating method and a plastic coating device for a steel pipe, and belongs to the technical field of steel pipe coating. The plastic coating method for performing plastic coating on the outer wall of the steel pipe comprises the following steps: heating the steel pipe to the preset temperature, rotating the steel pipe, and spraying an anticorrosion layer on the surface of the steel pipe; and transferring the sprayed steel pipe to a curing stage, wherein the steel pipe is equipped with a pipeline fixing device at the stage of transferring at least part of thesteel pipe; and the pipeline fixing device can enable the steel pipe not to be in contact with a conveying device so as to avoid damage to the anticorrosion layer on the surface of the steel pipe. Through the adoption of the plastic coating method, the damage to the anticorrosion layer not to be cured is prevented when the plastic-coated steel pipe is transferred, the degree of automation is high,the construction cost is low, the economic benefit is high, the method is simple, the surface of an anticorrosion pipeline manufactured by adopting the plastic coating method is uniform, the anticorrosion layer is firmly combined with the steel pipe, the anticorrosion layer is dense, wearproof and anticorrosive, and the service life of the anticorrosion pipeline is long.