Improvement for electrochemical luminescence (ECL) property of MgIn2O4 is attempted by partial exchange of Mg2+ ion in MgIn2O4 to Ca2+ ion. Mg1-xCaxIn2O4 solid solution was obtained in the region 0 < x < 0.4. Efficiency for ECL per unit current for Mg1-xCaxIn2O4:Er3+ increased with the increase in the ratio of Ca2+ ion, and showed a peak at x = 0.25 and then decreased steeply. ECL efficiency for other rare-earth ion-(RE:Sm, Eu, Ho) doped Mg1-xCaxIn2O4 also increased comparing with those for MgIn2O4:RE. This Ca2+ addition effect on the ECL efficiency seems to be caused by the improvement of the efficiency for the impact activation. (C) 2008 Elsevier B.V. All rights reserved.