This paper proposes a new method of busbar differential protection, which is deduced from conventional busbar differential protection by introducing busbar voltages and can eliminate the impact of asynchronous sample data. In order to analyze the characteristics of the proposed method, a PSCAD busbar simulation model based on real substation of Shaanxi grid is built. The simulations of internal and external faults show that, the conventional busbar differential protection will malfunction while using asynchronous sampling data, and the proposed method can operate correctly during same circumstances. Meanwhile, the proposed method can use the conventional busbar differential protection setting value directly. Therefore, it is easy to apply the proposed method in practice. This work is supported by National Natural Science Foundation of China (No. 51177127).