The novel SnO2:Sm3+,Zr4+ afterglow phosphor is synthesized by solid state reaction. The SnO2:Sm3+ doesn't show afterglow. But, after co-doping Zr4+ in SnO2:Sm3+, the red afterglow luminescence of Sm3+ is firstly observed and the important role of Zr4+ on the afterglow is investigated. The photoluminescence shows that the doping of Zr4+ increases the emission lines of Sm3+ and decreases the emission band due to trapped hole center. The thermoluminescence reveals that the co-doping of Zr4+ induces the increase of shallow traps corresponding to the thermoluminescence peak at 48 degrees C. The depth of the traps is calculated to be 0.61 eV. The positron annihilation indicates that the traps are due to negatively charged tin vacancies and they play the important role on the afterglow of Sm3+ as hole traps. (c) 2012 Elsevier B.V. All rights reserved.