Disclosed is a method for determining transmission power of a second TFCI bit indicating transport format information of data on a downlink shared channel transmitted from a selected Node B to a UE in a mobile communication system including the UE existing in a handover zone and a plurality of Node Bs in an active set of the UE. The Node Bs transmit dedicated channel data including a first TFCI bit to the UE over dedicated channels. A first Node B transmits dedicated channel data over a dedicated channel and transmits downlink shared channel data over the downlink shared channel. The first Node B determines a transmission power level of the second TFCI bit to be higher than a ratio of transmission power of the dedicated channel data from a Node B transmitting only the dedicated channel data to transmission power of the first TFCI bit.