Twenty kinds of oxides (Al 2 O 3 , CaO, Co 2 O 3 , Cr 2 O 3 , CuO, Fe 2 O 3 , GeO 2 , MgO, MnO 2 , MoO 3 , Nd 2 O 3 , P 2 O 5 , PbO, SiO 2 , SnO 2 , Ta 2 O 3 , TiO 2 , V 2 O 5 , ZnO and ZrO 2 ) were added into the intergranular regions of Nd 2 2 Fe 7 1 B 7 magnets and their effects on the coercivity, thermal stability and intergranular microstructure were investigated. It was found that (1) the coercivity is considerably enhanced by additions of MgO, Al 2 O 3 , Cr 2 O 3 , ZnO and CaO, but greatly decreased by ZrO 2 , TiO 2 , P 2 O and CuO; (2) the open circuit flux loss from room temperature to 200°C is decreased by additions of MgO and ZnO, slightly increased by CaO, Cr 2 O 3 and A 2 O 3 , and greatly increased by MnO 2 , ZrO 2 , TiO 2 and P 2 O 5 . Microstructural studies reveal that a new intergranular Nd-O-Fe-M phase with composition close to 70Nd-220-5Fe-(1-3M) (M = Mg, Zn, Ca, Mn, Zr, etc.) appears in the oxide-doped magnets. The variations in the magnetic properties arise from the occurrence of this Nd-O-Fe-M phase. By comparing the effects of the oxide additives with those of the element additives, it was also found that a small amount of oxygen in the intergranular regions is helpful in improving the coercivity and the thermal stability of Nd-Fe-B magnets.