Ce3+ and Eu2+ codoped calcium magnesium chlorosilicate Ca8Mg(SiO4)4Cl2 (CMSC) was synthesized for the first time. The diffuse reflection spectra,excitation and emission spectra of CMSC : Ce3+, Eu2+ were measured and studied. Due to the good overlap between the Ce3+ emission bands and Eu2+ excitation bands, the energy transfer between Ce3+ and Eu2+ ions is expected to be very efficient and is confirmed by the emission spectra of CMSC : Ce3+, Eu2+ system. The fluoresence lifetime of Ce3+ in CMSC : 0.006Ce3+ and CMSC : 0.006Ce3+, 0.03Eu2+ was determined to be 30.1 and 17.2ns,respectively. By the calculation,the probability of energy transfer from Ce3+ to Eu2+ (PSA) is 2.49 x 10(7)/s and energy transfer efficiency (eta(SA)) is 42.9%.