With the rapid development of the multi-cloud storage market, more and more users choose to store data in the cloud, followed by the explosive growth of duplicate data in the cloud environment. Because cloud service brokerages are independent of each other, traditional data deduplication can only eliminate redundant data on several cloud servers managed by the brokerages themselves. To further improve the data deduplication in a cloud environment, this study proposes a multi-brokerage joint deduplication scheme. Through the blockchain technology to promote the cooperation between cloud service brokerages and the construction of a brokerage alliance, the scope of data deduplication is extended from single brokerage managed clouds to multiple brokerages managed clouds. At the same time, it can bring win-win benefits to users, cloud service brokerages and cloud service providers. Experiments show that the multi-brokerage joint deduplication scheme can significantly improve the data deduplication effect and save network bandwidth.