The invention discloses a concrete additive capable of solidifying chlorions efficiently for a long time as well as a preparation method. A silicon aluminum phase component is added in the concrete additive capable of solidifying chlorions efficiently for a long time and accounts for 20 to 46.75 percent of the total mass of the concrete additive capable of solidifying chlorions efficiently for a long time; the silicon aluminum phase component is bentonite and/or kaolin which is calcined at 400 to 800 DEG C, the particle diameter is 80-um square hole sieve residue less than or equal to 10 percent and the mass percentage of Al2O3 is more than or equal to 35 percent; furthermore, the silicon aluminum phase component can generate Friedel salt (calcium chloraluminate hydrate) with the purity being more than 90 percent under the concrete alkaline environment. According to the concrete additive, the chlorions in the concrete can be solidified efficiently and stabilized for a long time, and the transmission speed of the chlorions in the concrete is effectively reduced. In conclusion, the technology has the technical advantages of low mixing amount (1 to 5 percent by mass of substituted gelmaterial), high chlorion solidification efficiency and long-term stable solidification effect.