The invention belongs to the technical field of electrical system databases, and discloses a heterogeneous data source unified joint query method. A data source interface is obtained, a standard SQL is subjected to grammar analysis, an SQL execution plan is generated, an SQL plan is executed, data of different data sources is loaded into memory, already loaded data is parallelly calculated, and acalculation result is returned back to a client side. The connecting frequency needed for inquiring all heterogeneous data sources is reduced, and requirements of joint query in all the heterogeneousdata sources can be met in a specific business scene.