Abstract: AIM: To search for more effective and less toxic new type radiosensitizer, three types of organic germanium sesquioxide were synthesized. METHODS: 1. Substituted cinnamic acid or substituted phenyl propynoic acid reacted with trichlorogermane to afford the addition products which were hydrolyzed to the corresponding germanium sesquioxide. 2. β trichlorogermyl propionyl chloride reacted with ethyl ester of leucine or phenyl alanine to give the products which were hydrolyzed to the corresponding germanium sesquioxide. RESULTS: Eight germanium sesquioxides were synthesized and seven of them are new compounds (2～8). The type of carboxy -β-(substituted phenyl) vinyl germanium is reported for the first time. The structures of the compounds have been elucidated by UV, IR,¹HNMR and elemental analysis. CONCLUSION: The synthetic compounds were tested for radiosensitizing activity, compound 4 exhibited significant radiosensitizing effect both in vitro and in vivo. Compound 4 showed great potential as a new type radiosensitizer with more effective action and lower toxicity.