A phosphor having a formula of TxEySizNrTbaLbMc is provided, in which T is Mg, Ca, Sr or Ba; E is Mg, Ca, Ba, Ti, Cu, Zn, B, Al, In, Sn, Sb, Bi, Ga, Y, La or Lu; L is Li, Na or K; M is Ce, Pr, Nd, Pm, Sm, Gd, Dy, Ho, Er, Tm, Yb or Mn; and 1.4≤x≤2.6, 0≤y≤0.5, 4.3≤z≤5.6, 7.4≤r≤9, 0.01≤a≤0.5, 0≤b≤0.5, 0≤c≤0.5, in which Tb ion is used as a luminescence center, and valence of the Tb ion is lower than 3+, and the phosphor is excited by an excitation light and has an emission band with a full width at half maximum greater than 50 nm. A method of forming the phosphor is also provided.