Abstract: Based on corrosion and protection mechanism of the tubing and casing,we developed a kind of annulus protectant formula system based on pyridine quaternary ammonium salt as the main agent.The performance evaluation results show that the annular protective agent has good resistance to corrosion,scale inhibition performance and sterilization ability for tubing,casing and rubber specimen,can effectively protect the ring casing space; Because of the addition of sulphur removal agent,its ability to resist hydrogen sulfide was enhanced.They can be applied to the oilfield brine with a density of 1.30—1.35 g/cm³ under different well depth conditions; The annulus protectants posses good thermal stability,high temperature resistance and can be used in high temperature deep wells.