The invention discloses a preservative for mineral based marine concrete. The preservative is prepared from, by weight, 5-10 parts of montmorillonite, 40-60 parts of kieselguhr, 10-20 parts of sepiolite and 5-15 parts of aedelforsite. The invention further comprises a preparation method and application. The preservative for the mineral based marine concrete can achieve quick-hardening and early-strength properties, can improve the erosion of a complex seawater environment where chloride ion, sulfate ion and carbonization coexist, and the non-cracking function is achieved; the preparation process is simple, the operation is convenient, the cost is low, and the preservative is suitable for large-scale promotion and application.