The invention discloses a dynamic monitoring method for a dam foundation rock mass construction process. The method comprises the following steps of step 1, detecting internal geological conditions of a dam foundation rock mass, and mastering development states and distribution rules of karst pores and karst caves; and performing three-dimensional imaging according to the geological parameters; step 2, importing a three-dimensional image into a BIM platform to generate a three-dimensional digital model; step 3, making a construction scheme in the BIM platform according to the three-dimensional digital model containing the geological information; step 4, according to the formulated construction scheme, performing concrete filling and grouting treatment on the karst pores and karst caves in the dam foundation rock mass; step 5, collecting internal geological parameters of the dam foundation rock mass after concrete filling and grouting treatment, generating a three-dimensional image, importing the three-dimensional image into the BIM platform, and detecting concrete filling and grouting effects; and step 6, if the effects are detected to be unqualified, adjusting a construction scheme in the BIM, adding seal holes, and performing leaking stoppage grouting till the effects are detected to be qualified; According to the method, dam foundation rock mass construction is efficient, accurate and refined, the problems of repeated operation and low production efficiency are solved, and the method has guiding significance for dynamic regulation and control of treatment measures and construction schemes of engineering.