The invention provides a preparation method of an enhanced aluminum calcium chloride crystal, which mainly solves the problems of special raw material requirements, high possibility of radiation pollution and poor water purification effect in flocculant preparation in the prior art. The method comprises the steps of: 1) preparing a magnesium ion aqueous solution, an aluminum ion aqueous solution, a calcium ion aqueous solution, a hydroxide ion aqueous solution, a surfactant aqueous solution and a sodium carbonate suspension, 2) mixing, heating and stirring the aluminum ion aqueous solution, the calcium ion aqueous solution, the hydroxide ion aqueous solution and the surfactant aqueous solution to prepare a multiphase aluminum calcium chloride suspension, 3) controlling pH (potential of hydrogen) of a reaction solution, mixing, heating and stirring the magnesium ion aqueous solution, the sodium carbonate suspension and the multiphase aluminum calcium chloride suspension to prepare an enhanced multiphase aluminum calcium chloride suspension, performing room temperature standing on the suspension, obtaining a precipitate of the suspension, and drying the precipitate to form the enhanced aluminum calcium chloride crystal. The method is simple in technology, nontoxic, environmentally friendly and low in cost; and the prepared material contributes to improving purification quality of sewage and can be used for water purification treatment.