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 Ymin=fmin(X) wherein X represents a reference resistance associated with a given electric trace segment, Ymin 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|≧Ymin, the to-be-tested via hole is a faulty via hole, and if |Xa−X|