Abstract: Cellulose acetate nanofibers(CANFs)were prepared by electrospinning cellulose acetate(CA), followed by deacetylation to obtain cellulose nanofibers(CNFs). Subsequentially, in-situ polymerization of polypyrrole was perform to fabricate the conductive composite nanofibers(CNFs-PPy), which was combined with cellulose paper as a flexible substrate for assembling a flexible pressure sensor. The materials were characterized by FT-IR, XRD and SEM, and the mechanical and sensing performance of the devices were analyzed using a universal material testing machine and an electrochemical workstation. The results showed that polypyrrole was successfully coated on the surface of cellulose nanofibers, and the nitrogen content of composite nanofiber was 24.8%. The current-voltage curves of the sensor maintained a good linear relationship under 1-15 kPa pressure load, and the relative current change rate increased with increasing pressure. The sensitivity values of the sensor were up to 1.77 kPa^-1 in the range of low pressure(0-0.99 kPa), 0.43 kPa^-1 in the range of medium pressure(1.00-8.33 kPa) and 0.22 kPa^-1 in high pressure(8.53-15 kPa), respectively. The sensor had excellent signal reliability and stability, i.e., the sensing signal remained stable after 3 000 cycles of loading. The sensor could realize the real-time monitoring of external pressure changes such as finger touch, which provided a new insights into the development of green electronics.