Abstract: In drilling operation,drilling fluid density in hole,which is not a constant but changing varying from temperature and pressure in super deep well under high temperature pressure condition,is a necessary basic data in various drilling construction and design.Therefore,it is necessary to study high temperature and pressure effects on drilling fluid density in super deep well.Influencing characteristics of temperature and pressure on water-based drilling fluid density in super deep well are measured by simulating experimental device of high temperature and pressure drilling fluid density and field preparation drilling fluid of super deep well in Shengke No.1 well.According to measuring results,density prediction model for water based drilling fluid under temperature and pressure influence is established.It shows that,the temperature effect is bigger than pressure effect on density of water based drilling fluid,and the decreasing amplitude of drilling fluid density is bigger with temperature and pressure enlarging.Meanwhile,the drilling fluid has better compressibility under high temperature and pressure.The prediction model established provides a new method for reasonable density range determination of field drilling fluid.