Objective To determine the acetylation level of nucleophosmin (NPM) in female breast cancer and to discuss its function through mutation of modified lysine sites. To construct positive and negative NPM mutants on its acetylated lysine sites and to express them in breast cancer cells.   Methods Acetylation level and acetylated lysine sites of NPM in three breast cancer tissues and para-carcinoma tissues were detected by acetylome technology; NPM mutants were constructed by site-directed mutagenesis PCR, specific PCR products were digested by DpnI and transformed into Escherichia coli(E.coli) to obtain specific plasmids for mutants; The accuracy of mutants were verified by double restriction enzyme digestion and sequencing; The mutants were expressed in BT-549 cells by transient transfection and verified by RT-PCR method. Protein expression and acetylation level of NPM were validated by Western blotting; Function of NPM acetylation was analyzed by proteomic detection and bioinformatic analysis.   Results The 27th and 32nd lysine of NPM were highly acetylated in breast cancer tissues, which were 2.76 and 2.22 times higher than those in adjacent normal tissues, respectively; The NPM mutants showed the same molecular weight as that of wild type NPM and contained expected mutation sites; Corresponding NPM mRNA levels of BT-549 cells transfected with NPM mutants were significantly increased. With the increase of wild type NPM expression level, NPM acetylation level increased, while decreased after 27th lysine underwent negative mutation. NPM acetylation can significantly change the expression levels of 101 proteins in BT-549 cells, which are enriched in regulation of cellular macromolecule biosynthesis, DNA-template transcription, RNA biosynthesis and RNA metabolism process.   Conclusion NPM is highly acetylated in breast cancer and can play a key role in cellular macromolecule biosynthesis, DNA-templated transcription, RNA biosynthesis and RNA metabolism process.