Abstract: The traditional noise figure cascading formula is only applicable to two-port network. Focusing on the active multi-channel receive system with unequal amplitude and phase superposition, a universal model is established and corresponding theoretical formula is derived. On this basis, the rationales of three test methods, which employ two-port test equipment to complete the noise figure measurement of multi-port network, has been deduced including the gain method, the branch method and the power divider method. Then comparative analysis is made in terms of operation complexity and test error, and the accuracy of the proposed theoretical formula and test approach is verified by simulation afterwards. This article will provide theoretical support for antenna pattern optimization and system link indicators allocation during system design, also a useful reference for system testing.