A signal detecting method and device for a multi-codeword multi-input multi-output (MIMO) system are provided, which are used in the field of communication and solve the problem that it is complex to implement a signal detecting method in the multi-codeword MIMO system and the error between the signal obtained through detection and the signal actually transmitted from the transmitting end is large. The method includes: converting a received complex number signal into a real number signal; performing channel estimation to obtain a channel matrix; correcting the channel matrix to obtain an equivalent corrected matrix; generating an equivalent detecting signal according to the equivalent corrected matrix and the real number signal obtained through conversion; quantizing the equivalent detecting signal to obtain an equivalent quantized detecting signal; and generating a signal transmitted from a transmitting end according to the equivalent quantized detecting signal. The method and device can be applied in a receiving device of a multi-codeword MIMO system.