a method of detecting faulty via holes of a printed circuit board . the printed circuit board including a number of electric trace segments . the method includes steps of : providing a testing system , the testing system comprising a processor , a storing means and a resistance measuring device , the storing means for storing a function y min = f min wherein x represents a reference resistance associated with a given electric trace segment , y min represents a minimum threshold value ; measuring a resistance of an electric trace segment of a to - be - tested printed circuit board using the resistance measuring device , a to - be - tested via hole located on the electric trace segment ; and judging whether the to - be - tested via hole is a faulty via hole according to the following criteria : if | xa − x |≧ y min , the to - be - tested via hole is a faulty via hole , and if | xa − x |& lt ; y min , the to - be - tested via hole is an acceptable via hole , wherein xa represents the measured resistance of the given electric trace segment counterpart of the to - be - tested printed circuit board .