The invention provides a preparation method of 1,4-benzdioxan-2-formic acid. The preparation method comprises the following steps: by taking benzylodiglycidyl ether and o-halogen phenol as raw materials, performing cyclization reaction, debenzylation reaction and oxidization reaction to obtain the 1,4-benzdioxan-2-formic acid. The preparation method provided by the invention is simple in reactionprocess; as the benzylodiglycidyl ether and the o-halogen phenol are used as the raw materials for reaction, no pollutants are produced, and no-irritative and no-allergic objects are produced; compared with other existing lines, the preparation method is environmentally friendly, high in total yield and favorable for mass production; the ee value of the finally prepared 1,4-benzdioxan-2-formic acid is more than or equal to 99 percent, and the chiral purity is high.