A method for preparing an electrostatic dissipative polymer and a blend of a thermoplastic polymer and the ESD polymer is disclosed. The method for preparing an electrostatic dissipative polymer includes the step of polymerizing the electrostatic dissipative polymer in the presence of a reactive solvent and lithium salt dissolved in the reactive solvent, wherein the amount of the reactive solvent is from 0.1 to 20 weight parts based on 100 weight parts of the produced electrostatic dissipative polymer, the amount of lithium salt is from 0.1 to 5 weight parts based on 100 weight parts of the produced electrostatic dissipative polymer, and the reactive solvent is aliphatic glycol having from 2 to 8 carbon atoms and having a primary alcohol group, or aromatic glycol having from 6 to 10 carbon atoms.