A method and system for over the air performance testing based on a multi-antenna system are disclosed. The method comprises: a branch device mapping path signals from a channel emulator to test antennas according to the set number of the combined sub-paths and sub-path mapping rule; the test antennas transmitting spatial signals according to the path signals from the branch device; and a device under test receiving the spatial signals; and an over the air performance analysis and display module analyzing and displaying the over the air performance of the device under test based on the spatial signals received by the device under test. The present invention implements the test of the over the air performance of a multi-antenna terminal.