Synthesis and luminescent properties of Ce(3+)-doped SrAlSi4N7 yellow-emitting phosphor are reported. In comparison with YAG: Ce(3+), the phosphor exhibits smaller thermal quenching and a broader emission band centering at 555 nm with a bandwidth as large as 115 nm, being suitable for fabricating high color rendering white LED. It is observed in material synthesis that intense luminescence can be achieved only in case of excessive AlN in the raw materials. The role of the excessive AlN is studied. The mechanism for existence of edge-sharing [AlN4] tetrahedral, which is unreasonable according to the aluminum avoidance principle, is discussed in detail.