The North Qilian ophiolites, with the characteristics mainly of MORB and boninite, were mostly formed at back arc and island arc environment and emplaced over island arc accretion wedge and active continental margin. So, It is possible that the North Qilian ophiolites similar to that of Cordilleran type by geochemical and emplaced characteristics. In North Qilian ophiolite belt, a volcanic sedimentary sequence lies conformably on the top of the ophiolite section, as in the Laohushan and Jiugequan area. The pillow lava at the top of the ophiolite is originated from the magma chamber beneath the spreading ridge, while the pillow lava in the overlying rock sequence is formed from partial melting of the depleted asthenospheric mantle off ridge, so they have different tectonic significance respectively. In the paper, the framework of plate tectonic of early Paleozoic North Qilian, and the periods and scale of North Qilian ocean basin were disccused. It can also be inferred that the North Qilian oceanic basin was a part of the Paleo Asian oceanic, and the scale of the North Qilian ocean basin was probably very large, and similar to that of today’s Pacific ocean.