Water-based varnish is prone to generate a lot of bubbles when it is processed or used. The bubbles can cause coating defects during coating, so the film quality is not very well. Adding defoamer in varnish can quickly eliminate the bubbles. Changing the type and amount of the defoamer prepared varnish and tested its defoaming properties to discussion the influence of defoamer on defoaming properties of water-based varnish. The results show that the performance of different defoamers defoaming is different, and Foamex 810 has the best defoaming properties. The amount of adding defoamer impacts defoaming properties to a certain extent. When water-based varnish added Foamex 810 with the amount of 1% in, the defoaming efficiency comes to the peak 96%.