The invention discloses a preparation method of a high-thixotropy early-strength type polycarboxylate superplasticizer. The preparation method comprises the following steps of (1) adding isobutene polyoxyethylene ether and/or isopentene polyoxyethylene ether, micromolecular polyether, unsaturated fatty acid glyceride, a quaternary ammonium salt monomer and an oxidant into water, and stirring the mixture under 15 to 30 DEG C until the mixture is dissolved; (2) preparing a first solution by a reducing agent and water, preparing a second solution by a chain transfer agent and the water, and preparing a third solution by unsaturated monocarboxylic acid, an unsaturated carboxylic ester monomer and the water; (3) dropping the first solution, the second solution and the third solution in materials in step (1) within 3 to 4 hours at the same time, and carrying out a heat-preservation reaction for 1 to 1.5 hours under 35 to 40 DEG C after dropping is completed; (4) adding an alkaline modifier to neutralize the pH (Potential Of Hydrogen) to be 6 to 7 after the reaction of the materials in step (3) is completed, thus obtaining the high-thixotropy early-strength type polycarboxylate superplasticizer. The high-thixotropy early-strength type polycarboxylate superplasticizer prepared by the invention has an excellent thixotropic property.