Abstract：More than 99% purity of liquid crystal intermediate of 4-ethoxy-2,3-difluorophenyl acetic acid was synthesized via alkaline hydrolysis and acidification after Willgerodt-Kindler reaction with 4-ethoxy-2,3-difluoroacetophenone as the starting material. The target compound was characterized by 1HNMR、IR and GC-MS. The results of condition experiments showed the effect of Willgerodt-Kindler reaction was best when the molar ratio of 4-ethoxy-2,3-difluoroacetophenone/sulfur/morpholine was 1:2:4, the reaction temperature was 105～115 ℃ and the reaction time was 2 h.The mass ratio of the main product was 71.54%,the mass ratio of the by-product of 4-ethoxy-2-morpholine-3-fluoro-phenyl thiomorpholine amide was 14.60%.The generation reason of the by-product during Willgerodt-Kindler reaction was proposed according to the results of experiments,and its structure was confirmed by 1HNMR and GC-MS.