The invention provides a pre-processing method and system of a Gerber file, and a polishing and brushing method of a PCB (printed circuit board). The pre-processing method includes the following steps that: all electrical wires on the surface layer of the PCB, of which the linewidth is smaller than a preset threshold value, are searched and positioned in the Gerber file; for each electric wire of which the linewidth is smaller than the preset threshold value, whether the electric wires are suspended wires is judged; if the electric wires are suspended wires, teardrops are added at the suspended ends of the suspended wires; and if the electric wires are not suspended wires, the method terminates. The polishing and brushing method of the PCB includes the following steps that: a PCB is arranged in a manner that the PCB is tilted by 45 degrees; and polishing and brushing processing is performed on the PCB. According to the processing on the suspended wires in the Gerber file in the invention, modification is slight, and therefore, engineering confirmation time can be decreased; and the teardrops are added at the suspended ends of the suspended wires, so that the suspended wires will not tend to be deformed due to brushing in a subsequent polishing and brushing process.