The embodiment of the invention provides a superposition transmission method using codebook-based closed-loop precoding and a superposition transmission device thereof and a method for decoding signals in superposition transmission using codebook-based closed-loop precoding and a device thereof. The superposition transmission method comprises the steps that multiple code words for first user equipment are generated; at least one code word for second user equipment for pairing with the first user equipment is generated; the multiple code words for the first user equipment are mapped to multiple transmission space layers having the same number with that of multiple transmitting antennas; at least one code word for the second user equipment is mapped to at least one space layer of multiple transmission space layers; and superposition transmission for the first user equipment and the second user equipment is performed on at least one space layer. According to the method and the device, pairing of the user equipment having the same pre-coder and different rank indicators is realized so as to perform superposition transmission.