The invention relates to a double-channel reforming process method for an excitation system AC side excitation current sampling circuit. a group of AC side excitation current sampling current transformers CT is added in hardware, the design is concise, the structure is reasonable, each channel can use a group of completely-independent AC sampling current transformers CT, completely independent control on two channels can be realized, hidden safety dangers brought by sampling of a single group of current transformers CT are eliminated, the excitation system reliability and generating set operation reliability are improved, and the method can be widely applied to a UN5000 excitation system.