The invention discloses a new method for synthesizing nelarabine. According to the new method for synthesizing nelarabine, vidarabine is taken as a raw material, and acetylization, methoxylation, nitration and reduction reactions are carried out, so that the target product nelarabine is obtained with the total yield of 52%. The new method for synthesizing nelarabine has the greatest advantages that all the prepared nelarabine is beta configuration, and a tedious step of separating isomers in the traditional method is omitted; meanwhile, the raw material is a common chemical material, so that the raw material is available; and the operation is simple and convenient, the column chromatography isolation is not needed to be carried out in the whole course, and industrialization and expanded production are easy to realize.