The present invention relates to a method for preparing a styrenic olefin. The method of the present invention comprises the steps of: adding a catalyst and a solvent in a reactor and heating the reactor to create a reflux state; adding an alcohol starting material to the reactor dropwise at a constant rate; removing water generated by adding the alcohol starting material from the reactor, and purifying the obtained styrenic olefin. The method of the present invention is advantageous in minimizing byproducts and preparing styrenic olefins having a variety of substituents in high yield.