Multifunctional complex additive is a new drilling composite material of organically modified bentonite developed for drilling in the complex formation. The successful application of multifunctional complex additive in Yitanghu district ZK11-1 hole of Dunhuang indicates that it has effective wall protection and anti-pollution ability, with which the saturated brine drilling fluid prepared can be used for drilling in salt-gypsum stratum such as rock salt, sylvite and carnallite.