The total and single-differential cross sections of electron-impact ionization of lithium-Like Ions are investigated through the multi-configuration Dirac-Fock method (MCDF) and two-potential distorted-wave approximation. The calculation includes the cross-sections for a dozen of selected nuclear with charge Z between 4≤Z≤92, and incident energy from 1.05 to 15 or to 35 units of ionization energy. The calculated results are compared with the published theories and with experiment. The relativistic effects and the QED effects make a significant contribution to the cross sections at high incident energy and highly charged ions.