Abstract: Organic room-temperature phosphorescent (RTP) materials are simple to prepare, rich in types, low in toxicity．RTP materials have broad applications in display, sensing, and biological imaging．Most organic RTP materials show a phosphorescent lifetime of < 10 ms, but those with longer phosphorescent lifetime of > 100 ms have advanced and wider applications as their phosphorescence decay is visible to the naked eye．This paper reviews molecular design strategies of organic RTP materials with high quantum efficiency and long lifetime．Introduction of heavy atoms, formation of host-guest materials, construction of H-aggregation, formation of hydrogen bonds, design of donor acceptor (D-A) structures are emphasized．