The organic semiconductors have attracted much attention for plastic electronics due to their good solution processability, low temperature deposition, and compatible with large-area printing technology. The charge transport properties of polymer based field effect transistors are limited by their amorphous domains and weakly interaction between polymer chains. In this study, antisolvent like methanol is introduced to promote polymer chain aggregation, and slot die coating is used to finely tune the film morphology. The effects of anti-solvent introduction and slot die coating process on the device performance, e.g. charge transport, surface morphology, and solid state packing, were investigated in details. By optimizing the antisolvent ratio and polymer chain aggregation, the charge transport properties of the polymer devices were observed to be significantly improved. An average charge carrier mobility of 3.76 cm2 V−1 s−1 and a maximum mobility of 4.10 cm2 V−1 s−1 were achieved under optimized conditions. The controlling the aggregation degree by combining the mixed solvent system and slot die coating technique provides a convenient and practical approach to achieve high performance polymer field effect transistor.