The self-polymerized multi-pore polydopamine (MPDA) were prepared by soft template method. The porous structure brings a larger specific surface area to the MPDA (25.1 m2 /g), which also provides more adsorption sites on the material surface for the adsorption of water molecules. By controlling the reaction conditions, the polymer materials were screened and coated it on the quartz crystal microbalance (QCM) substrate. Among them, the QCM-MPDA sensor with the best performance was tested in the full humidity range (1% RH-95% RH). The results show that the prepared QCM-MPDA humidity sensor has small hysteresis (3.66% RH), short respond/recovery time (12 s/39 s), excellent long-term stability and good linearity and other humidity characteristics. Especially, it shows excellent response to ultra-low relative humidity (RH) environments. Between 1% RH and 10% RH, the sensor sensitivity is 12.38 Hz/% RH. The lowest detection limit of the QCM-MPDA sensor can reach 1% RH. Therefore, the potential application of self-polymerized multi-pore polydopamine modified QCM sensor in the field of humidity sensing can be expected in the future.