Electron donor (D) acceptor (A)-type conjugated polymers (CPs) have emerged as promising semiconductor candidates for organic field-effect transistors. Despite their high charge carrier mobilities, optimization of electrical properties of D A-type CPs generally suffers from complicated post-deposition treatments such as high-temperature thermal annealing or solvent-vapor annealing. In this work, we report a high-mobility diketopyrrolopyrrole-based D-A-type CP nanowires, self-assembled by a simple but very effective solvent engineering method that requires no additional processes after film deposition. In situ grown uniform distinct edge-on chain orientation that is beneficial for lateral charge nanowires at room temperature were shown to possess transport between source and drain electrodes in FETs. FETs based on the polymer nanowire networks exhibit impressive hole mobility of up to 4.0 cm(2) V-1 s(-1). Moreover, nanowire FETs showed excellent operational stability in high temperature up to 200 degrees C because of the strong interchain interaction and alignment.