The invention relates to micro-etching treating fluid. The micro-etching treating fluid comprises 30.0-60.0 g/L of sulfuric acid, 10.0-20.0 g/L of hydrogen peroxide, 0.1-1.0 g/L of hydrogen peroxide stabilizer, 2.0-5.0 g/L of inhibitor and 1 L of added water. The inhibitor is selected from the triamine base substituted phenol or the triamine base substituted thiophenol. The above micro-etching treating fluid is used for printed circuit board OSP pretreatment, a clean and rough copper surface can be formed, a protection film can be formed in combination with a copper face in the micro-etching process, the copper face electron supplying speed during the copper-gold electrochemical reaction is reduced, accordingly the potential difference between the copper and the gold is reduced, the biting corrosion rate of a copper welding pad is reduced, generation of the galvanic effect is restrained to the maximum degree, the phenomena of the color difference, area reduction or line excessive corrosion or even biting off cannot happen to the copper face connected with the gold face and obtained after micro-etching treatment, and meanwhile the phenomenon of coloring after OSP treatment can be effectively prevented from happening to the copper surface.