The invention discloses a method for synthesizing a neodymium phosphate solution and the synthesized neodymium phosphate solution. The method comprises steps as follows: a saturated metal halide salt water solution is prepared from metal halide salt; acidic phosphate ester and an organic solvent are mixed, a phosphate ester solution is obtained, and the volume ratio of acidic phosphate ester to the organic solvent is (1:2)-(1:20); neodymium oxide solid powder is added to the phosphate ester solution and stirred, and a turbid liquid is obtained and heated to 20-50 DEG C; the saturated metal halide salt water solution is added to the turbid liquid, heated and stirred, molecular sieves are added, the mixture reacts at the temperature of 20-70 DEG C for 20-90 minutes, is left to stand for layering after the reaction ends and then is separated, an oil phase, namely, the neodymium phosphate solution is obtained, and the mole ratio of metal halide salt to acidic phosphate ester is controlled to range from (1:5) to (1:50). The neodymium phosphate solution contains a little non-rare-earth metal phosphate, can reduce the viscosity of a glue solution in the polymerization catalysis process of synthetic rubber and reduces production loss; the molecular weight distribution of the synthetic rubber is widened, and the processability of the rubber is improved.