The invention provides lanthanum zirconate-based ceramic granulated powder for atmospheric plasma spraying and a preparation method thereof. The preparation method comprises the steps that mixed materials with the particle size of 60 nm or below are pressed into blocks, the material point distance among powder particles is reduced, the content of pores is reduced, and the densification is improved; mixed oxide blocks are obtained, and a solid phase reaction in the following sintering process is conducted smoothly and conveniently. In combination of the sintering process, the solid phase reaction of different oxides in the mixed materials is achieved, a lanthanum zirconate-based material is obtained and further crushed, low-speed sanding with low energy consumption is conducted at first, the loss of grinding bodies is reduced, the preliminary refinement of the larger sintered particles after sintering is achieved, and further refinement is facilitated; in combination with high-speed sanding at the second stage, nano-powder is obtained, the dispersion is good, the particle size is even, and the granulation requirements are met. Subsequently, in strict accordance with a defined granulation mode, the ceramic granulated powder meeting APS requirements is obtained.