A method of inhibiting an irregular aggregation of a nanosized powder includes (A) providing a nanosized ceramic powder to perform thereon a thermal analysis and thereby attain an endothermic peak temperature; (B) performing an impurity-removal heat treatment on the nanosized ceramic powder at a temperature higher than the endothermic peak temperature; (C) switching the nanosized ceramic powder from a temperature environment of the impurity-removal heat treatment to an environment of a temperature higher than a phase change temperature of the nanosized ceramic powder, followed by performing a calcination heat treatment on the nanosized ceramic powder in the environment of the temperature higher than the phase change temperature of the nanosized ceramic powder, wherein the nanosized ceramic powder skips the temperature environment between impurity-removal heat treatment and calcination heat treatment to shun generating a vermicular structure, avoid crystalline irregularity and abnormal growth, reduce particle aggregation, and achieve satisfactory distribution.