The invention discloses a catalyst carrier grain size control method. The method includes the following steps that firstly, with aluminum hydroxide dry colloid serving as the raw material, micelle is formed under the action of an acid peptizing agent, wherein the water content of the micelle is 40-60(wt)%; secondly, the micelle is subjected to extrusion forming through a single-screw or double-screw extruder; thirdly, a formed carrier enters a vibratory or rotary drying device through a conveying belt to be pre-dried, the water content of the carrier is controlled to be 45-55wt%, and a granular catalyst carrier is obtained; fourthly, the granular catalyst carrier is dried and roasted.