The invention belongs to the technical field of humidity sensors, and particularly discloses a preparation method and product of a quartz crystal microbalance humidity sensor. The method comprises thefollowing steps: S1, preparing a seed layer, namely depositing a Cu seed layer on a quartz crystal microbalance to serve as a humidity-sensitive layer material for subsequent growing a super-hydrophilic nano-wire; S2, preparing the humidity-sensitive layer, namely placing the quartz crystal microbalance deposited with the Cu seed layer in a NaOH and (NH4)2S2O4 mixed solution to grow a super-hydrophilic Cu(OH)2 nano-wire on the Cu seed layer to obtain a quartz crystal microbalance humidity sensor device. The product comprises a quartz crystal microbalance, the seed layer arranged on the frontside and/or back side of the quartz crystal microbalance and a nano-wire growing on the seed layer. The humidity sensor formed by the method has a response speed less than 1 second, and has the characteristics of high response, high sensitivity, good repeatability, stable performance and the like.