Abstract: In order to solve the problems of the traditional humidity sensor, such as the complex manufacturing process and the need for wired connection signal, this paper proposes a chipless RFID humidity sensor based on paper substrate. In order to improve the resonant characteristics of the paper based resonator, the distributed metal fragments loaded inside the asymmetric open ring are selected as the sensor structure, and the polyvinyl alcohol (PVA) is used as the humidity sensitive material. The structure of the sensor is optimized by genetic algorithm and HFSS software RF simulation. The sensor samples are prepared by inkjet printing technology, and PVA films with concentration ratios of 5%, 10% and 15% are prepared on the sensor surface by droplet coating method. The results of simulation and test show that the synergistic effect of PVA and paper base can obviously improve the sensitivity of the sensor. With the increase of PVA concentration, the sensitivity of the 15% PVA humidity sensor can reach 12.22 MHz/ %RH, but with the increase of PVA concentration, the recovery performance of the 5%PVA humidity sensor is poor, and the recovery performance of the 5%PVA humidity sensor can reach 83.87%. The PVA paper based humidity sensor has good temperature stability and medium and long term stability. Compared with similar research results, the PVA paper based humidity sensor developed in this paper has advantages in terms of humidity sensing range and sensitivity, and the manufacturing process is simpler, which provides the possibility of large-scale use of low-cost humidity sensor.