An acetic acid dropping device is characterized in that the device comprises a liquid level indicator, an acetic acid barrel and a ball valve, the liquid level indicator is arranged on the barrel wall of the acetic acid barrel, a hole is opened on the bottom of the acetic acid barrel, and the ball valve is arranged on the bottom of the acetic acid barrel by the hole. The pH value of plain boiled water is conveniently adjusted to make the pH value of the plain boiled water lie in optimum glass fiber dispersing range, glass fibers are uniformly dispersed, and the glass fiber wet process felt made has good practicability and high quality and is of high grade.