In this paper, there are three specimens of head shields possessing the external skeleton, collected from the purple red muddy limestone of the Qiaerbake Formation, early Late Ordovician, from the Yijianfang section of Bachu County, Xinjiang Autonomous Region. Among these specimens, the external morphological characteristics of the orbits (orb), pineal body (pi) are preserved on the one of the head shields (no.7 19 8), but the armour plates are absent on another two head shields. There are oral (Or) and the six pairs of the external branchial openings (bro2~7) outward independently opening on ventral shield of the fish bodies. In addition, the differences and similarities between the Ordovician and the Silurian—Devonian agathans possessing the external skeleton are discussed. Since there is no the naso hypophysial openings (nhypo) on the fossils, which possess six pairs of external branchial openings on the branchial region of the ventral aspect on the head shield. Therefore the Ordovician vertebrates of Bachu County should be a special and independent palaeotological vertebrate fauna. The paper is for the first time reporting the early vertebrate of the Ordovician possessing external skeleton, since Cambrian vertebrates fossils have no external skeleton in China up to now. This study is of great implication for understanding the early vertebrate's developing and evolution, and for establishing phylogenetic analysis on the basis of vertebrate biology.