The invention discloses a method for preparing vinyl acetylene by employing ultrasonic enhanced acetylene dimer. The adopted catalyst belongs to a nieuwland catalyst; the ratio of cuprous chloride to ammonium chloride to hydrochloric acid to water is 30.75kg to 15.67kg to 0.3L to 45L; the acetylene dimer reaction process is carried out in a reaction device with an ultrasonic wave; the power of the ultrasonic wave is 120W; the frequency is 40kHz; and the method comprises the following steps: (1) firstly, adding ammonium chloride and water to the reaction device, and introducing nitrogen, so as to stir bubbles during discharging air; (2) adding cuprous chloride and hydrochloric acid to the reaction device, further introducing nitrogen and stirring bubbles; and (3) replacing nitrogen with acetylene, further stirring bubbles, and starting the ultrasonic wave device, so as to prepare the vinyl acetylene in a manner of enhancing the acetylene dimer reaction. Compared with the prior art, the selectivity of the vinyl acetylene disclosed by the invention is greatly improved; the conversion rate per pass of the acetylene and the single pass yield of the vinyl acetylene are improved to different extents; and in a word, the comprehensive benefits of the method are relatively high.