The invention provides a method for establishing a power grid big data warehouse based on a CIM model, which comprises the following steps of: reconstructing a CIM model based on a database table structure of a plurality of existing power grid service systems; converting and storing the data in the plurality of existing power grid service systems and the ECIM to establish a power grid large data warehouse according to the reconstructed CIM model as a standard, which reduces the human intervention in the process of creating the power grid big data warehouse, when there are multiple database types, the creation of a large data warehouse can still be achieved more efficiently and stably, especially based on the CIM model, to realize the automatic creation of large data warehouse. In addition,the related metrics and attribute and relation metrics algorithm of this patent are applied to make entity merging more accurate and efficient. Meanwhile, the data cleaning and merging are processedin different cycles, avoiding the possible access conflict of large data warehouse.