Abstract: As one of the important exploration and development blocks in the northwest oil field, most of the wells exist Permian in the Tuoputai block at Tahe oilfield, with depth of about 4 500-5 200 m and thickness of 50-300 m. The loss is severe when drilling during the Permian, at the same time, parts of the non-Permian wells are also leaking severely in Tahe 10 and 12 blocks, which increase the difficulties in normal drilling, delay drilling time, it will lead to complex underground accidents, and has great influence of well cementing etc.in the late homework. The fly ash low density cement slurry system was prioritized to plug the Permian in this paper. The density of the slurry system is 1.60 g/cm³, the strength of compression is 6-8 MPa. It could add 5 mm and 10 mm fiber in the cement slurry when the leakage is severe. The fiber is bridged in the crack to form the structure of net space, and improved the plugging effect as well. Through plugging operations of several wells in the field, it could effectively improve the bearing capacity of the formation, greatly saved the drilling cycle and created favorable conditions for the later drilling and cementing construction.