A method for handling a soft buffer size by a user equipment, UE, in a wireless communication system, wherein the UE is connected to both a long term evolution, LTE, system and a new radio access technology, NR, system in dual connectivity, the method comprising: Determining a first UE capability for the LTE system and a second UE capability for the NR system; determining a total soft buffer size based on the first UE capability and the second UE capability; and sharing the total soft buffer size between the LTE system and the NR system based on at least one of a maximum transport block size, TBS, per transmission time interval, TTI, and a number of carriers used in the NR system, wherein the sharing the total soft buffer size between the LTE system and the NR system comprises: determining a required soft buffer size for the NR system based on at least one of the maximum TBS per TTI and the number of carriers used in the NR system; and assigning a soft buffer size which is remained after subtracting the required soft buffer size for the NR system from the total soft buffer size to the LTE system, wherein the required soft buffer size for the NR system is reported to a network, wherein the first capability for the LTE system is defined based on a UE category in the LTE system or a peak data rate in the LTE system, and wherein the second capability for the NR system is defined based on a peak data rate in the NR system. Determining a first UE capability for the LTE system and a second UE capability for the NR system; determining a total soft buffer size based on the first UE capability and the second UE capability; and sharing the total soft buffer size between the LTE system and the NR system based on at least one of a maximum transport block size, TBS, per transmission time interval, TTI, and a number of carriers used in the NR system, wherein the sharing the total soft buffer size between the LTE system and the NR system comprises: determining a required soft buffer size for the NR system based on at least one of the maximum TBS per TTI and the number of carriers used in the NR system; and assigning a soft buffer size which is remained after subtracting the required soft buffer size for the NR system from the total soft buffer size to the LTE system, wherein the required soft buffer size for the NR system is reported to a network, wherein the first capability for the LTE system is defined based on a UE category in the LTE system or a peak data rate in the LTE system, and wherein the second capability for the NR system is defined based on a peak data rate in the NR system. determining a required soft buffer size for the NR system based on at least one of the maximum TBS per TTI and the number of carriers used in the NR system; and assigning a soft buffer size which is remained after subtracting the required soft buffer size for the NR system from the total soft buffer size to the LTE system, wherein the required soft buffer size for the NR system is reported to a network, wherein the first capability for the LTE system is defined based on a UE category in the LTE system or a peak data rate in the LTE system, and wherein the second capability for the NR system is defined based on a peak data rate in the NR system.