The invention discloses a preparation method of a high-purity porous ceramic abradable seal coating and belongs to the technical field of seal coatings. High-purity ceramic powder containing no pore former and having doublet grain size distribution property is adopted as a raw material, the high-purity porous ceramic abradable seal coating having high porosity and bonding strength is prepared through a high-energy plasma spraying process, the anti-sintering performance of the coating is effectively improved, thus the use temperature of the coating is improved, and the service life of the coating is prolonged.