With solid-state reaction method, series of Y4Si2O7N2:Tb3+ phosphors were prepared under the high-temperature and high-pressure conditions. The photoluminescence properties at room and high temperature were investigated. Two groups of emission lines have been observed, which are corresponding to Tb3+ D-5(3) F-7(J) (J=6, 5, 4, 3, 2) and D-5(4) F-7(J) (J=6, 5, 4, 3) transitions. The physical mechanisms for excitation, emission, concentration quenching, and thermal quenching were investigated. The cross-relaxation mechanism between the D-5(3) and D-5(4) emission was investigated and discussed. The Tb-Tb critical distance for cross-relaxation was calculated to be similar to 13 angstrom. The optimum Tb3+ concentration in this phosphor is 15mol%. The quadrupole-quadrupole interaction dominates the non-radiative energy transfer between the Tb3+ luminescence centers and causes the concentration quenching. This phosphor shows high thermal stabilities that at 150 degrees C the intensity remains 92% compared with that measured at room temperature. The present work suggests that this Tb3+-doped Y4Si2O7N2 material is a kind of potential green-emitting phosphor.