The invention belongs to the technical field of synthesis of compounds and particularly relates to a preparation method of pentaerythritol triacrylate. The preparation method comprises the following steps: (1) dissolving pentaerythritol and sodium hydroxide into an organic solvent, and carrying out heating reflux in water so as to prepare pentaerythritol trisodium salt; (2) cooling pentaerythritol trisodium salt, adding a polymerization inhibitor, then dropwise adding an acryloyl chloride solution, and continuing to carry out reflux; and (3) washing and drying an obtained organic phase, so as to obtain pentaerythritol triacrylate. According to the preparation method, pentaerythritol triacrylate can be quantitatively synthesized, synthesized pentaerythritol triacrylate is high in purity and yield, the operation is simple, the reaction is easily controlled, and the process is reliable.