The invention relates to an early strength type water reducer and a preparation method thereof. The preparation method comprises steps as follows: acrylic acid, sodium methallyl sulfonate, 2-acrylamide-2-methylpropane sulfonic acid, acrylamide and water are mixed to obtain a solution A; a reducer, a chain transfer agent and water are mixed to obtain a solution B; polyether and water are mixed andheated, an initiator is added, the mixture is stirred, the solution A and the solution B are added, the mixture is heated for polymerization, a regulator is added to adjust the pH value to 6-7, and apolycarboxylate water reducer is obtained; a high polymer dispersant, calcium silicate, calcium nitrate, aluminum nitrate and water are mixed, the mixture is heated and stirred, a sodium silicate water solution is added, and a nano crystal nucleus early strength agent is obtained; the polycarboxylate water reducer and water are mixed, stirred and heated, the nano crystal nucleus early strength agent is added, the mixture is heated and stirred, and the early strength type water reducer is obtained. The early strength type water reducer is used for concrete and can make concrete have short setting time, high early strength and excellent work performance and adaptability.