Abstract: Based on the mapping of the Liaohe Group in the central segment of Jiao-Liao-Ji structural belt in the past several years, this paper mainly presents the implications of structural deciphering work applied to the metamorphic area geological mapping, which include the following five aspects:①As the significant geological boundary between the groups cannot be easily recognized, the authors emphasize the function of structural deciphering work when it is used to trace the hidden boundary; ②Different rock units or formations are often mixed with each other due to later deformation, and structural deciphering therefore should be used in this situation to distinguish different rock units (strata); ③Structural deciphering work must be carried out to trace all the different structural styles and deformation stages; ④Evaluation of the thickness of strata in the metamorphic area should be considered through structural deciphering work in the first time; ⑤The combination of deformation and metamorphism is very important in metamorphic mapping area. In all, structural deciphering is a useful tool to figure out the true geological fact in a metamorphic mapping area.