The conventional 40Ar/39Ar age of muscovite in high-pressure metamorphic orthogneiss, surrounding rocks of the Qinglongshan eclogite, is identical with its Rb-Sr and Sm-Nd ages. The Laser microprobe analysis shows that the argon isotope is evenly distributed in the muscovite. The preliminary conclusion is (1) muscovite in high-pressure metamorphic orthogneiss does not contain excess argon and can be the object for 40Ar/39Ar dating; (2) muscovite in the Qinglongshan eclogite contains large amounts of excess argon while muscovite in its surrounding rocks, i. e. high-pressure orthogneiss, does not contain excess argon. This fact proves that the excess argon of muscovite in eclogite does not come from its country rocks but from its inheritance.