A method and apparatus for monitoring downlink control information (DCI) in a wireless communication system, especially in a new radio access technology (NR) is provided. A user equipment (UE) monitors first DCI having a first size in a UE specific search space (USS). The first size is determined based on an active bandwidth part (BWP). The UE further monitors second DCI having a second size in a common search space (CSS). The second size is determined based on a default BWP.