The invention discloses a silica-glass micro-defect detecting method. The method includes the following steps that two light transmitting faces of a silica-glass sample are accurately polished; the polished silica-glass sample is corroded with an acid solution; after being corroded for 0.5-2 hours, the silica-glass sample is taken out and cleaned with deionized water, and the silica-glass sample is observed and detected with a microscope; according to the steps, the silica-glass sample is repeatedly corroded and observed till defects in the silica-glass sample are observed, or till defects are still not observed when the residual thickness of the silica-glass sample is 20-30 microns. By means of the silica-glass micro-defect detecting method, the micro-defects in silica glass can be detected.