A method performed by a BS for handling repetitions of transmissions is provided. The method includes transmitting an RRC configuration including a first parameter configured with a first value and a second parameter configured with at least one second value; and transmitting DCI on a PDCCH scheduling a PUSCH transmission. The DCI enables the UE to select one of the first parameter and the second parameter to determine a number of PUSCH repetitions; determine the number of PUSCH repetitions as the first value when the first parameter is selected; determine the number of PUSCH repetitions as one of the at least one second value indicated by the DCI when the second parameter is selected; and perform the PUSCH transmission for a number of times based on the number of PUSCH repetitions. A BS using the aforementioned method is also provided.