We present a promising solution-processed vertical transistor which exhibits high output current, high on/off current ratio, and low operation voltage. Numerous poly(3-hexylthiophene) vertical channels are embedded in vertical nanometer pores. Treating the sidewalls of pores by self-assemble monolayer with long alkyl chains enhances the pore-filling and inter-chain order of poly(3-hexylthiophene). The channel current is therefore greatly increased. A grid metal inside the porous template controls the channel potential profile to turn on and turn off the vertical transistor. Finally, the transistor delivers an output current density as 50-110 mA/cm 2 at 2 V with an on/off current ratio larger than 10 000.