Preparation method of -[1,2-ethanediylbis(oxy-2,1-ethanediyl)] ester

The invention discloses a preparation method of -[1,2-ethanediylbis(oxy-2,1-ethanediyl)] ester. According to the preparation method, gaseous phosgene and diethylene glycol serve as the reaction raw materials, a -[1,2-ethanediylbis(oxy-2,1-ethanediyl)] ester product serves as solvent, and the -[1,2-ethanediylbis(oxy-2,1-ethanediyl)] ester product of which the content is larger than 98.5% and the yield is larger than or equal to 99.0% is prepared, wherein the gaseous phosgene is subjected to low temperature liquefaction and gasfication to remove a trace amount of tar and metal impurities and then subjected to concentrated sulfuric acid washing to remove a trace amount of water. The total content of metal of iron, chromium and nickel in -[1,2-ethanediylbis(oxy-2,1-ethanediyl)] ester is decreased to 1.0 ppm or below, and the water content is 0.01%. According to the preparation method, the reaction is conducted completely, the yield is high, byproduct bipolymer and metal impurities are greatly reduced, the product