The spectroscopic and molecular properties of CSe(X1Σ+) radical are investigated using the complete active space self-consistent field (CASSCF) method followed by the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach. The potential energy curve (PEC) is calculated over the internuclear separation range from 0.08 to 2.5 nm at the basis sets, aug-cc-pV5Z for C and aug-cc-pV5Z-pp for Se atom. The spectroscopic parameters (D0, De, Re, ωe, ωexe, αe and Be) of six isotope molecules (12C74Se, 12C76Se, 12C77Se, 12C78Se, 12C80Se and 12C82Se) are evaluated using the PEC of CSe(X1Σ+) radical. The spectroscopic parameters are compared with those reported in the literature, and excellent agreement is found between them. With the PEC of CSe(X1Σ+) radical obtained here, a total of 81 vibrational states of 12C80Se species are predicted when J = 0 by numerically solving the radical Schrödinger equation of nuclear notion. For each vibrational state of every isotope species, the vibrational levels, classical turning points and inertial rotation constants are reported, which are in agreement with the available experimental data.