Future organic field-effect transistors (FETs) may utilize one-dimensional (1D) semiconductor materials in their channels. In this study, we used the ab initio method to explore the transport characteristics of 1D nanowire polythiophene FETs comprehensively. Based on the 2028 map in the International Technology Roadmap for Semiconductors (ITRS) in 2013, our theoretical simulations showed that n-type and p-type gate-all-around (GAA) 1D polythiophene FETs with 5-nm gate length (Lg) and appropriate underlap (UL) satisfy the basic high-performance and low-power-consumption device applications. Moreover, both the n-type and p-type GAA 1D polythiophenee FETs (Lg = 3 nm) meet the high-performance needs of ITRS. Our numerical results revealed that the organic transistors can be designed by using a single nanowire and the minimum Lg of transistors can scale to 3 nm.