A method for transmitting and receiving a downlink channel in a wireless communication system and a device therefor are disclosed. Specifically, a method of receiving, by a user equipment (UE), a downlink channel in a wireless communication system, the method comprising receiving configuration information related to a plurality of control resource sets, wherein an index of a control resource set group associated with each control resource set is indicated based on the configuration information; and receiving (i) a first downlink channel based on a first control resource set and (ii) a second downlink channel based on a second control resource set, wherein, based on that an index of a first control resource set group associated with the first control resource set is not indicated, the index of the first control resource set group is set to 0.