As the information processing part in flexible integrated sensor systems, there are several basic requirements for the integrated circuits (ICs) in addition to flexibility, including high speed, low power consumption, medium to large scale integration, etc. Currently there is no solution that can meets all the requirements. Here we present our recent progress in high-performance flexible thin film transistors based on carbon nanotube (CNT). The transistors exhibit large on-state current, high mobility (>80 cm²V^-1s^-1), small subthreshold slop (<70 mVdec^-1), and large current on/off ratio (>10⁵), all with an operating voltages of 2 V. The developed fabrication approach presents high yield and the transistors’ performances are highly uniform with well controlled threshold voltage distribution, which enable the realization of various logic gates and the most complex CNT-based ICs on flexible substrate. Finally, an integrated smart sensor system with in-situ signal processing capability for human body monitoring based on CNT was demonstrated.