Abstract: The laminated limestone, dike rock and tuff are associated in the upper part of Middle Permian Nuo Ribagaribao Formation in the Zhou Qiongmalu area, northern Qiangtang. The plots of Al-Fe-Mn triangle diagram show that two limestones lay in the area of hydrothermal sediments. The average ratio of Fe/Ti、(Fe+Mn)/Ti and Al/(Fe+Mn+Al) are 0.53,41.90 and 46.06, respectively; the rate of Ni /Co is less than 3.6 and U/Th is less than 1; These rocks are enriched in various degrees in metal elements(Co,Cu,Zn and Pb) and hydrothermal active elements(As,Sb and Ba).The rare earth elements distribution patterns of these rocks show weak negative δCe and δEu , and skew to the right. Besides, the Co,Ni,Fe in limestones and the volcanic rocks on Co/Y-P/Y, Ni/Y-P/Y and Fe/Y-P/Y are present well linear dependence. Above all, those characteristics show that the limestones of Middle Permian Nuo Ribagaribao Formation are hydrothermal sedimentation and are formed in the environment of back-arc basin. This discovery has some indication meaning to the research of the large-scale Pb,Zn geochemical anomaly and the further ore-prospecting work in the upstream of the Tuotuohe area.