Abstract: For the purpose of cementing in high pressure gas and saltwater layers,the ultra-high density slurry system was studied.The slurry system with density up to 2.60-2.85 g/cm3 has been developed with novel ultra-high density weighting materials,superfine weighted stabilizer and other fillers by grading of grain.It is characterized by good fluidity,high strength,high temperature resistance,and strong anti-channeling,and can realize safe self-adaptive operation as the temperature and density change,without ultra-retarding at the top.Additionally,further study has been made by designing the mixing program of ultra-high density cement samples for field operation,constantly simulating transportation of such samples and optimizing the plan,the cementing technology with ultra-high density slurry has been formed.It has been successfully used in Well Guanshen-1,a key exploratory well of Sinopec,with average density of spacers of 2.75 g/cm3 and average slurry density of 2.78 g/cm3,creating a record of the highest density of slurry in China.