A user equipment and a method for handling a switching time period of downlink (DL)-uplink (UL) switching for half duplex-frequency division duplex operation are provided. The method includes: receiving a first configuration for a first active bandwidth part (BWP) with a first sub-carrier spacing (SCS), the first active BWP being one of an active UL BWP and an active DL BWP; receiving a second configuration for configuring a second active BWP with a second SCS, the second active BWP being another one of the active UL BWP and the active DL BWP; receiving a third configuration for the switching time period, the switching time period having a unit of symbol; performing communication with a Base Station (BS) on the first active BWP with the first SCS; and performing, after the switching time period, communication with the BS on the second active BWP with the second SCS.