A method of performing channel estimation of a physical downlink control channel (PDCCH) in a wireless communication system is disclosed. Specifically, the method performed by a user equipment (UE) includes receiving a synchronization signal block (SSB) from a base station, receiving system information (SI) from the base station based on the SSB, transmitting a physical random access channel (PRACH) preamble to the base station, receiving a response to the PRACH preamble from the base station, transmitting UE capability information related to the channel estimation to the base station, receiving information for a PDCCH monitoring duration from the base station, and performing the channel estimation based on the information for the PDCCH monitoring duration. The UE capability information includes information for a maximum number of control channel elements (CCEs) that are capable of the channel estimation per PDCCH monitoring duration.