The invention relates to a preparation method of ethylene glycol allyl ether in the technical field of chemicals. The method is characterized by adopting allyl alcohol and ethylene oxide as main raw materials to firstly carry out polymerization reaction in a reaction kettle in the presence of a catalyst to obtain a coarse product, purifying the coarse product through neutralization, rectification and rectification at reduced pressure, and collecting fractions to obtain ethylene glycol allyl ether with purity being not less than 99%. The method has the beneficial effects that the method is simple and practicable, the cost is low, few by-products are produced, no sewage is discharged, excessive allyl alcohol is recycled, and the method is suitable for large-scale industrial production of ethylene glycol allyl ether.