The invention relates to the technical field of building additives and in particular to a low-surface tension hyperbranched shrinkage reduction type polycarboxylate superplasticizer and a preparationmethod thereof. The preparation method comprises the following steps: putting an unsaturated polyether, a polyhydroxy polymer and a hyperbranched shrinkage reduction functional monomer and water intoa container, mixing at 20-60 DEG C, adding an initiator solution, a chain transfer agent solution and an unsaturated acid solution, keeping the temperature for a certain time, and adjusting the pH value of the obtained reaction product to 6.0-7.0 by using an alkali substance, thereby obtaining the low-surface tension hyperbranched shrinkage reduction type polycarboxylate superplasticizer. As a great amount of the shrinkage reduction functional monomer is introduced into a polycarboxylic acid molecular structure through copolymerization, the polycarboxylic acid molecular structure has a shrinkage reduction function chain segment, a steric hindrance segment and an adsorption group segment, the prepared superplasticizer product has low surface tension, unification of shrinkage reduction and dispersing performance of concrete can be achieved with a low doping amount, the concrete can be prevented from shrinkage cracking, then the durability of the concrete can be improved, and practical application values are great.