Abstract: Four kinds of density functional theory（DFT） methods（B3LYP,BLYP,BP86,and B3P86） are employed to predict the molecular structures and adiabatic electron affinities of Si_n/Si^-_n（n=7¹0） species.The basis set is double-ζ plus polarization quality with additional s-and p-type diffuse functions,labeled as DZP++.The ground states of Si₇/Si^-₇,Si₈/Si^-₈,Si₉/Si^-₉,and Si₁₀/Si^-₁₀ are D_5h（（）¹A′（）₁）/D_5h（（）²A″（）₂）,C_2h（（）¹A_g）/C_3υ（（）²A₂）,C_s（（）¹A′）/C_s（（）²A′）,and C_3υ（（）¹A₁）/C_3υ（（）²A₁） respectively.Compared with the experimental values,the BLYP method is the best for electron affinities.The electron affinities corrected by zero-point vibrational energies for Si₇,Si₈, Si₉,and Si₁₀ are 1.90,2.59,2.07,and 2.20 eV,respectively.