A virtual branch control method is proposed to solve the branch power flow off-limit problem. By adding a shunt virtual branch to the branch experiencing branch power flow off-limit， the original off-limit current of the branch can be reduced to a target level of branch current. The admittance of the virtual branch can be obtained by target shunting coefficient， Thevenin's equivalent impedance and admittance of the branch of power flow off-limit. Based on substitution theorem， the virtual branch is replaced by a parameterized virtual power source. Thus， the remove problem of virtual branch is turned to injection power increase problem on the two buses connected by the virtual branch. Based on sensitivity of the apparent power of the branch with respect to bus injection power， the minimum cost control scheme for branch of power flow off-limit can be obtained. The simulation results of the New England 39-bus test system show that the current of the branch of power flow off-limit descends to target level of current. The feasibility and efficiency of the proposed algorithm are validated.