Vienna rectifier is a boost-type rectifier with unidirectional energy flow, which is widely used in many applications. Under unbalanced grid, there will be even harmonics in dc-link voltage and odd harmonics in input current if the traditional control methods are used. Therefore, two control methods for Vienna rectifier under unbalanced grid are introduced, which are balanced positive-sequence current control and instantaneous active power control. The current zero-crossing distortion (CZCD) is an inherent issue for Vienna rectifier due to its special circuit topology. The displacement angle between the input current and the voltage is revealed, which is the essence of CZCD. The issue of CZCD is more complex under unbalanced grid than that under balanced grid, and CZCD cannot be addressed well under existing suppression method. A novel method that can minimize CZCD under unbalanced grid is also proposed. The proposed method works well under both balanced and unbalanced grid. Finally, an experimental platform is built, and the feasibility and superiority of the proposed method are verified by comprehensive experiments.