High proportion of renewable power systems are prone to voltage-dominant faults in the process of cascading failures，requiring a reasonable allocation of reactive power compensation to provide voltage support capability. In view of voltage-dominant faults，a reactive compensation optimization allocation method considering voltage-dominant cascading failures is proposed. Firstly，the voltage-dominant cascading fault scenarios are extracted by simulating cascading failures；Then，a collection of typical scenarios is obtained by clustering the topological structure；After that，the installation of minimum reactive compensation and minimum load loss under each scenario is taken as the objective function，a distributed robust optimization model is constructed，and the column and constraint generation algorithm is adopted for iterative solution of the model. Finally，the rationality and effectiveness of the proposed method are verified through numerical examples. The results of the examples show that the proposed method can effectively optimize the allocation of reactive compensation for key nodes in voltage-dominant cascading faults.