CaAl2O4- based phosphors with Eu2+ and La3+ codoped have been prepared by the traditional solid-sintering method, and the photoluminescence intensity can be efficiently enhanced by codoped La 31 ions. Positron annihilation spectroscopy proves that a large amount of V''(Ca) vacancies exist in the CaAl2O4 host and the complex defects 2La(Ca)(center dot) V ''(Ca)] form on increasing the concentration of doped La 31 ions. The thermoluminescence spectra demonstrate that some new trap levels with various trap depths are produced on increasing the concentration of the doped La 31 ions, which are correlated to the La3+- associated complex defects in the CaAl2O4- based phosphor.