With the access distributed generation such as photovolatic and energy storage systems, the voltage of the distribution network fluctuates frequently. To solve the uncertainty issues caused by widespread distributed generators, a decentralized robust voltage control is proposed considering the uncertainties of distributed generation clusters. It aggregates large-scale decentralized resources into clusters to perform decentralized voltage control. First, in view of the complex structure of the network and the wide range of generators, a clustering method based on the improved Louvain algorithm is proposed. This further considers the voltage sensitivity and capacity of distributed generators in its modularity function. Second, since the power flow of the distribution network is more variable with distributed generators, a decentralized robust control method considering the uncertainties of the voltage sensitivity is proposed on the basis of cluster divisions. The voltage fluctuations caused by uncertainties such as model parameters and power fluctuations can be suppressed by coordination of controllable clusters. Finally, the feasibility and effectiveness of the proposed method is verified by case studies.