ErGa3-xMnx disordered alloy is successfully prepared by the vacuum arc melting technology,and the crystal structure and magnetic properties are investigated by using the x-ray diffraction and magnetic measurements.The Rietveld structural analysis indicates that the ErGa3-xMnx crystallizes into a cubic structure with space group of Pm(3)m in Mn doping range of x=0-0.1.However,the disordered alloy with structural formula of Er0.8GaⅠ2(GaⅡ,Mn)0.4 as the second phase is separated from cubic phase for the samples with x =0.2 and 0.3,which is induced by substituting the (GaⅡ,Mn)-(GaⅡ,Mn) pair at 2e crystal position for the rare earth Er at la site.The lattice parameters tend to increase with Mn content increasing due to the size effect at Ga (1.30 (A)) site by substituting Mn (1.40 (A)) for Ga.The paramagnetic characteristic is observed by doping Mn into ErGa3 at room temperature.With Mn content increasing from x =0 to 0.1,the magnetic susceptibility x tends to increase.This phenomenon can be due to the increase of effective potential induced by doping Mn into ErGa3.However,the magnetic susceptibility x continues to decrease with the increase of Mn content in a range ofx ＞ 0.2,which is due to the phase separation from the cubic Er(Ga,Mn)3 to the hexagonal Ero.8Ga2(Ga,Mn)0.4.