The invention relates to an ultrasonic atomizing device and an atomizing method thereof, in particular to an ultrasonic atomizing device and an atomizing method for a liquid-containing binder for glass cotton. According to the device, the coordinated function of air pressure atomizing and ultrasonic vibration atomizing is used, and a flow adjusting needle valve or an anti-blocking removing valve is selected to adjust the flow of the binder and prevent the binder from blocking. When the binder with a certain viscosity is sprayed out, a good atomizing effect is realized as the particle size of the liquid-containing binder is small, the usage rate of the binder is effectively improved, the production cost is reduced, meanwhile, the liquid-containing binder is more uniformly dispersed in glass fibers, the color difference of the glass cotton product is reduced and the tear strength of the glass cotton product is effectively improved.