Two monoxides of typical smaller chlorofullerenes, (#271)C50Cl10O and (#913)C56Cl10O, featured with double-fused-pentagons, were synthesized to demonstrate further regioselective functionalization of non-IPR (IPR = isolated pentagon rule) chlorofullerenes. Both non-IPR chlorofullerene oxides exhibit an epoxy structure at the ortho-site of fused pentagons. In terms of the geometrical analysis and theoretical calculations, the principles for regioselective epoxy oxidation of non-IPR chlorofullerenes are revealed to follow both "fused-pentagon ortho-site" and "olefinic bond" rules, which are valuable for prediction of oxidation of non-IPR chlorofullerenes.