Abstract: Taking Malus robusta as the test material, a pot experiment was used to set five Mn treatment levels(0,1,10,100,200 mg·kg^-1),which were labelled as CK,Mn1,Mn10,Mn100,and Mn200,respectively.The effects of exogenous Mn application on Mn subcellular distribution, mineral elements, polyamine content, polyamine metabolizing enzymes and their related enzyme gene expression in Malus robusta were investigated, in order to provide reference for the detoxification mechanism of Mn in Malus robusta.The results showed that, compared with CK,the proportion of Mn in the cell wall and organelles gradually increased, and the proportion of Mn in the cytoplasm gradually decreased as the addition of exogenous Mn increased.Meanwhile, the high levels of Mn significantly reduced the Mg, Na, K and Ca contents of the plants and increased the Zn.Furthermore, the HPLC results showed that, except for spermine（Spm）,which was significantly increased in insoluble covalently bound polyamines（PIS-PAs）,the putrescine（Put）,spermidine（Spd） and and Spm contents of other polyamine fractions showed a decreasing trend, which was both related to the activity of polyamine metabolizing enzymes（ADC,ODC,DAO,PAO） and polyamine metabolizing enzyme genes（PavADC,PsaODC,ParDAO,PavPAO 2）.In conclusion, the Mn subcellular distribution and plant nutrient homeostasis of Malus robusta roots were influenced by exogenous Mn application, and the polyamine content, polyamine metabolizing enzymes and their related genes were involved in the detoxification process of Malus robusta under Mn stress.