Abstract: A novel humidity microsensor with high sensitivity, short response time and good reproducibility was developed for measuring the plant leaf surface humidity. The sensor utilized single-port surface acoustic wave resonator (SAWR) with resonance frequency of 433 MHz as the basic component. The SAWR structure was fabricated on the ST-cut quartz substrate with a zero temperature coefficient to avoid temperature effect. The silicone-containing polyelectrolyte was electrosprayed onto the SAWR surface to form micro/nano-scale polymer particle clusters film as the humidity-sensitive material. The preliminary experimental results show that the humidity microsensor has a good performance with wide detection range from 10% to 97% RH, high sensitivity of 500 Hz/%RH, rapid response time of 5 s and up-to 3% RH measurement accuracy.