The invention discloses a 
triamcinolone acetonide acetate particle, and a preparation method and a medicinal composition thereof. The preparation method comprises the following steps: 1) heating and dissolving 
triamcinolone acetonide acetate with 
aqueous solution of 
ethanol, naturally cooling the obtained solution to obtain 
acicular crystals, washing away the 
ethanol from the crystals with water for injection, 
drying the washed crystals, and then adding the crystals into water for injection at a temperature of 0 to 10 DEG C; 2) linearly adding dropwise 
triamcinolone acetonide acetate solution dissolved with 
dimethyl formamide solution into the 
mixed solution of the water for injection at the temperature of 0 to 10 DEG C obtained in the step 1), simultaneously stirring the 
mixed solution, keeping the temperature of the 
mixed solution at 0 to 15 DEG C, and continuing stirring the mixed solution for 1 to 30 minutes to obtain a mixture of water and crystals; and 3) as usual, filtering the mixture of the water and the crystals obtained in the step 2) and vacuum-
drying the obtained crystals. The invention adopts a 
crystal inoculation process, thus crystals of the prepared 
triamcinolone acetonide acetate particles have regular shapes and uniform particle sizes; 
crystallization is free from jet milling and the physicochemical property of the particle is stable; and no 
crystal expansion phenomenon generates in the prepared 
triamcinolone acetonide acetate suspension injection during storage.