A method and apparatus for assigning a power of a master cell group (MCG) and a secondary cell group (SCG) in dual connectivity in a wireless communication system is provided. A user equipment (UE) receives a configuration for a minimum power per CG from a network, and assigns the power per CG based on the received configuration. In this case, at least one of the MCG or the SCG is configured with at least one timing advance (TA).