This paper proposes a new smart sensor for the detection of damage in structures using mechanoluminescence (ML) material SrAl2O4:Eu (SAOE). SAOE is a kind of functional ceramics that can emit visual light when it is subjected to external mechanical action. The luminescence of SAOE is very high so that it enables us to view the visual light with naked eye. A smart film sensor is fabricated using SAOE powder and polymer. The effect of load frequency on the emitted visual light is investigated under cyclic loading conditions. Furthermore, detection of a crack and evaluation of the stress concentration and stress intensity factors are performed using SAOE film sensor. Experimental results demonstrate that the visual light emitted by SAOE film sensor has good correlation with the equivalent strain and stress.