The present disclosure relates to the technical field of fine chemical engineering, and particularly discloses a stepwise solidus synthesis method for a micro-mesoporous calcium aluminate catalyst, comprising: mixing a calcium oxide-based powder with an alumina-based powder and an adhesion pore-enlarging agent; pelleting and molding the mixture; pyrolyzing and coking the pelleted and molded product in a rotary kiln reactor under the conditions including an outlet reaction temperature of 300° C.˜500° C. and a residence time of 0.2˜3.5 h; and subsequently carrying out a solidus reaction in an internal heating rotary kiln reactor under the conditions including an outlet reaction temperature of 900° C.˜1,500° C. and a residence time of 0.1˜5 h to produce calcium aluminate; decomposing and gasifying the pyrolyzed char in the calcium aluminate to promote the formation of pores, thereby producing micro-mesoporous calcium aluminate catalyst; wherein the weight ratio between the calcium oxide-based powder and the alumina-based powder is within a range of 12:(2˜15), the added amount of the adhesion pore-enlarging agent accounts for 0.1˜15% by weight of a total amount of the calcium oxide-based powder and alumina-based powder; wherein the weight of the calcium oxide-based powder is calculated based on calcium oxide, and the weight of the alumina-based powder is calculated based on alumina. The calcium aluminate catalyst prepared with the method provided by the present disclosure has advantages of large specific surface area, low density and high strength.