Some C-benzylated flavonoids based on gericudranin A were synthesized and evaluated their cytotoxic activities for the elucidation of structure-activity relationship. 2,4,6- Trihydroxyacetophenone was converted to target molecules in $6{sim}7$ steps via sequential protection, aldol condensation, cyclization, regioselective C-benzylation, and deprotection. The cellular growth inhibition of the synthetic C-benzylated flavonoids was investigated against sixteen human cancer cell lines. Among these compounds, 5b showed the most potent cytotoxicities against several cell lines, especially as potent as adriamycin against SNB19 cell lines with an $IC_{50}$ value of $0.7{mu}M$.