Abstract: On the basis of the studies on tectonic deformation and metamorphism of the Err x Compressed Zone in northern Xinjiang and comparison between the Ertix Compressed Zone and Irtys Compressed Zone in USSR, the age of strata within the Ertix Compressed Zone is discussed in this paper, and it is proposed that the metamorphosed strata could not be Late Carboniferou; but Precambrian and Early-Middle Paleozoic in age except the fossil-bearing and unmetamorphoaed strata whose ages are Late Carboniferous and Early Permian because the P and T conditions were not sufficient to cause the Upper Carboniferous to be metamorphosed up to amphibolite facies and even to be migmatized when metamorphism took place at the end of the Late Carboniferous. It is necessary to map in detail the Ertix Compressed Zone and to make geochronological researches on the metamorphosed strata in order to determine their protolith age and metimorphie age.