A new green light emitting long lasting afterglow CaSnO3:Tb phosphor was prepared by a traditional solid-state reaction method. The duration can reach nearly 4 h in the light perception of the dark-adapted human eyes (0.32 mcd m(-2)). The luminescent properties and thermoluminescence curves were investigated. One model named "reversible energy transfer" was proposed to explain the mechanism of the occurrence of long afterglow. (c) 2005 Elsevier B.V. All rights reserved.