A communication device for handling a transmission in an unlicensed band comprises a storage unit for storing instructions and a processing means coupled to the storage unit. The processing means is configured to execute the instructions stored in the storage unit. The instructions comprise performing a first transmission using a hybrid automatic repeat request (HARQ) process in a first subframe of an unlicensed band to a network; receiving a first DCI for the HARQ process in a first control channel in a second subframe of the unlicensed band in response to the first transmission from the network, wherein a distance between the first subframe and the second subframe greater than four subframes; and performing a second transmission using the HARQ process in a third subframe of the unlicensed band to the network according to the first DCI.