A series of post_orogenic granite plutons occur on the southern margin of Altay orogenic belt. A gneissic deformed granitic pluton occurs in the Ertix faulted zone to the south of Fuyun, intruded by an underformed granitic pluton. The former pluton is datedby U-Pb TIMS method at 281±5 Ma and the latter at 275±2 Ma. These data indicate that shearing deformation still took place to some extent along Ertix zone during ca. 280～275 Ma in the post-orogenic period. The deformation probably ended or became much weaker after 275±2 Ma.