Abstract: Borehole stability and drill fluid performance stability remains to be a contradiction, while it’s essential to better resolve this problem for the development of drilling fluid technology. The various drilling fluid systems used domestically are all electronegative, i.e., the ξ potential is a negative value. This type of drilling fluid has stable performances while it does no good to borehole stability, and causes drilling problems frequently. Electropositive drilling fluid system can be used to keep the wellbore stability, improve ROP and protect oil/gas reservoirs. This paper focuses on the transmission of drilling fluid electrical property, formula of electropositive drilling fluid and field test, and it proves that besides its inhibition to clay hydration and dispersion, the electropositive drilling fluid can also improve the salt and calcium pollution resistance of drilling fluid, and good for reservoir protection.