Structure and properties of the ground states and low-lying excited electronic states of CH, NH and OH radicals are reported in this paper using CCSD(T) method and aug-cc-pVTZ basis set.Their analytic potential energy functions are in good agreement with the Murrell-Sorbie function, and the ground states are X2Π for CH, X3Σ- for NH and X2Π for OH radicals, and the adiabatic excitation energies of a4Σ- and 6Σ- for CH, a1Δ and 5Σ- for NH, a4Σ- and 6Σ- for OH are 0.705, 7.669, 1.895, 3.492, 4.535 and 14.041eV, respectively.