Low-density cement paste for salt-cavern gas storage well cementation

The invention discloses a low-density cement paste system for salt-cavern gas storage well cementation. The low-density cement paste system is composed of an oil well cement, a superfine cement, a lightening admixture, a salt resisting and water-loss reducing agent, a defoamer and a saline, and used for gas storage well cementation in a rock salt formation. Due to use of a special salt resisting ingredient, the corrosion of the cement paste to the wall of a salt deposit well is retarded, adverse impact of the salt rock diffusing to the cement paste on the properties of the cement paste is reduced, and such technical problems affecting the quality of sealing and cementation in well cementation as retarded coagulation and extra retarded coagulation of cement paste, and low strength of set cement are well solved.