The output of quartz crystal microbalance (QCM) sensors is in the form of frequency signals. These sensors offer advantages such as low cost, fast response, and high sensitivity. This study utilized porous α-Al2O3, a moisture-sensitive material, to enhance the humidity detection sensitivity of QCM sensors. Simulations were performed using COMSOL, by applying the QCM sensing principle, to investigate the influence of various structural dimensions on the sensor’s resonant frequency, quality factor, and admittance, while optimizing its geometric parameters.Subsequently, the sensitivity and dynamic characteristics of the sensor were examined over a specific humidity range. The experimental findings demonstrate the remarkable humidity discrimination capability of the sensor,with a maximum frequency response of 13 kHz, sensitivity of 155 Hz/(%RH), and response and recovery times of 20 s and 8 s, respectively. These results demonstrate the reliability and accuracy of the QCM sensor, utilizing porous α-Al2O3 as the moisture-sensitive material, in humidity detection.