Thirty-four polymerid trilobite species as- signed to thirty-three genera belonging to seventeen families are described from the Cambrian Ni- danshan and Liudaogou groups at two localities in the Lajishan Range of the Qilian Mountains, Hua- long, northeastern Qinghai Province. Four species are new and sixteen species are in open nomenclature. The new species are identified as Paranomo- carella dingmaoshanensis sp. nov., Adelogonus oblongus sp. nov., PLacosema qinghaiense sp. nov. , and Meteoraspis qinghaiensis sp. nov. , and the species in open nomenclature are referred to Fuchouia , Idamea , Prochuangia , Maotunia , Proasaphiscus, Paradistazeris, Probilacunaspis, Lisaniella , Luyanhaoaspis, Neosolenopleurella , Xintaia, Fatocephalus, Paracoosia, Procerato- pyge, and Onychopyge respectively. As reported by Zhou et al. hansi-font-family: calibri; mso-hansi-theme-font: minor-latin">(1996hansi-font-family: calibri; mso-hansi-theme-font: minor-latin">), from Laijishan Range the polymerid trilobites are in association with agnostoid trilobites belonging to a large number of genera, indicating the Cambrian trilobite fauna from the Lajishan Range is rather highly diverse. The trilobite fauna has affinity with Cambrian tri- lobite taxa described from the Jiangnan Slope Belt, South China, and the slope areas of the Tarim Block, NW China, including notably Wanshania wanshanensis , Grandioculus truncatus , Iniotoma porosus , Hua yuanella zhiqiangi , Jimachongia lata , Luyanhaoaspis, Paracoosia , Proceratopyge, Prochuangia, Fuchouia, Fatocephalus, Placosema and AdeMgonus. Revisions and emendations are made to some of early published taxa.