The nitrides Ca2Si5N8:0.5%Eu2+, x%Tm3+(x = 0, 0.5, 1, 2, 4) (CSN:0.5E, xT) phosphors were prepared via the high temperature solid-sintering method using CaH2 as calcium source. These phosphors exhibited strong orange long-lasting phosphorescence (LLP) after turning off the activating light. Besides, the CSN:0.5E, 1T phosphor with an afterglow time of more than 200 min (0.32 mcd/m2). Furthermore, the temperature-dependent emission spectra of CSN:0.5E, 1T were investigated from temperature 80–500 K and an anti-quenching phenomenon that the emission intensities increased then decreased under excitation at increased temperature was found. Ultimate, the proposed mechanism on temperature dependence of luminescence was analyzed. This study provides a new perspective for the impact of temperature-dependent problem as a consequence of heating processes in luminescent materials.