Quantum-chemical calculations on some derivatives of [n]-prismanes expanded by ethynyl or ethenyl groups have been performed using density functional theory (DFT) method.Their geometric structures,electronic structures,vertical ionization potentials and vertical electron affinities have been obtained at the B3LYP/6-31G** level of theory.Meanwhile,the total strain energy has been investigated in detail and compared with [n]-prismane and other derivatives.The present paper has also computed the enthalpies of formation for different isomers so as to evaluate their thermal stabilities. Quantum-chemical calculations on some derivatives of [n] -prismanes expanded by ethynyl or ethenyl groups have been done using density functional theory (DFT) method.Their geometric structures, electronic structures, vertical ionization potentials and vertical electron affinities have been at at the B3LYP / 6-31G ** level of theory. Meanwhile, the total strain energy has been investigated in detail and compared with [n] -prismane and other derivatives. The present paper has also computed the enthalpies of formation for different isomers so as to evaluate their thermal stabilities.