Molecular doping is effective method for changing the electrical and physical properties of organic semiconductors. However, the mechanism of doping process was not certainly discovered and moreover the doping efficiency of the donor-acceptor copolymer was low. Herein, we synthesized diketopyrrolopyrrole based donor-acceoptor copolymers and investigated the doping efficiency of each polymer by UV-Vis, FT-IR, and EPR spectroscopy. The TBD2F polymer which added thiophene linker with DPP based polymer, could be doped effectively by F4TCNQ molecular dopant. Moreover, the 2D-GIXD was measured to analyze the do-pant position at polymer crystalline phase. From the result we could speculate that by dopant located at alkyl chain region of polymer crystalline matrix, the efficient doping enabled.