Abstract: Prior art defense is an act that the accused infringer who confronts the alleged infringement can put forward that what he uses is prior art to counterwork the alleged infringement of rightful owners and claim that he does no infringements. It uses the right barrier mode， on the basis of which mode， article 62 of the Patent Law should be revised as follows: in dispute of patent infringement， if the accused infringer has evidence that can prove what he uses are prior arts or prior designs， what he does is not infringement act. In practice， we must first compare the accused art with the implicated patent technology， then with prior arts.