Among the leading energy materials, metal tri-halide perovskite quantum dots (PQDs) with outstanding optoelectronic properties are at the forefront of current research. However, enormous challenges remain to be addressed, including hazardous components and poor stability, before achieving practical applications of PQDs. Although there are diverse methods to improve the stability of PQDs, it is of central importance to avoid damage during operation. Herein, we develop a pre-protected strategy in which the coating combines the advantages of doping with sodium ions to jointly improve stability. Because the stable Na-rich surface acts as a defence, it protects the PQDs from damage during the coating process; therefore, they retain their initial fluorescence. When employing these Na-rich PQDs as core materials of a coating, the highly fluorescent Na: CsPb(Br,I)3@Al2O3 nanocomposites can maintain good stability even when directly immersed in water or exposed to illumination. Clearly, the combination of these features sheds light on the stabilization and applications of PQDs.