The invention discloses solid chlorine sterilization algicide and a preparation method thereof. The solid chlorine sterilization algicide mainly comprises the following components by weight: 35 to 55 parts of sodium dichloroisocyanurate, 5 to 10 parts of sodium chlorite, 5 to 10 parts of ion-type surface active agent such as dodecyl benzene sulphonic acid, 10 to 25 parts of sodium gluconate, 10 to 25 parts of anhydrous magnesium sulfate or anhydrous calcium sulfate and 4 to 8 parts of sodium chloride. The preparation method comprises the following steps: the ion-type surface active agent such as the dodecyl benzene sulphonic acid, the dodecyl benzene sulphonic acid, the anhydrous magnesium sulfate or anhydrous calcium sulfate and the sodium chloride of the selected parts are respectively arranged inside a drying device to be dried, the dried parts are mixed with sodium dichloroisocyanurate and the sodium chlorite to be smashed into powder mixture, then the powder mixture is sent to a tablet machine to be formed, and then the formed product is inspected, weighed, divided and vacuum packed to obtain the finished product. The solid chlorine sterilization algicide has simple preparation process and has the advantages of high efficiency, wide application, non-toxicity, environmental protection, economical efficiency and the like.