Over the past few decades, low phosphorus removal efficiency hampered the further application of constructed wetlands (CWs). In this study, magnesium (Mg)-containing materials, i. e., magnesia and magnesite, were added into CWs substrate to improve TP removal performance. Results showed that the average TP removal efficiency of magnesia group (MA-CW) reached 93.3%, which was 17.5% and 18.6% higher than that of magnesite group (ME-CW) and control group (QZ-CW), respectively. P fractionation analysis showed that the proportion of phosphorus sequestration by substrate in MA-CW was 90.4%, while it was only 65.1% and 58.8% in ME-CW and QZ-CW, respectively. Phosphorus assimilation by plant in ME-CW accounted for 9.52%, higher than other groups, which was attributed to the stimulated plant growth caused by Mg addition. The average total chlorophyll content of plants in ME-CW was 4.61 mg g-1 FW during the study period and the plant growth rate was superior to other groups, whereas in MA-CW, excessive alkaline (pH= 10.29) caused by MgO dissolution depressed plant growth. Mg addition also elevated the absolute abundance of (PAOs), which followed the order of MA-CW (1.76 +/- 0.03x107 copies g(-1)) > ME-CW (1.35 +/- 0.02x107 copies g-1) > QZ-CW (4.48 +/- 0.13x106 copies g(-1)). Characterization of magnesia and magnesite before and after phosphate adsorption was compared and the results indicated that phosphorus adsorption by magnesium mainly relied on coprecipitation of Mg-3(PO4)(2) and MgHPO4, as well as ligand-exchange on the surface.