Multiple　vibration　modes　of　an　engineering　structure　might　be　excited　by　earthquake　ground　motions.　Multiple　tuned　mass　dampers　(MTMDs)　are　widely　used　to　control　these　multi-mode　vibrations.　However,　in　the　commonly　used　MTMD　system,　the　mass　element　in　each　tuned　mass　damper　(TMD)　is　normally　assumed　to　be　the　same.　To　improve　the　performance　of　MTMDs　for　seismic-induced　vibration　control,　non-uniform　MTMD　masses　are　adopted　in　the　present　study　to　improve　the　mass　utilization　of　TMD,　and　a　location　factor　is　proposed　to　determine　the　best　location　of　each　TMD　in　the　MTMD　system.　The　effectiveness　of　the　proposed　method　is　validated　through　numerical　study.　The　results　show　that　the　proposed　method　effectively　reduces　the　seismic　responses　of　the　structure　induced　by　multiple　vibration　modes.