The present invention discloses an information transmission method, a device, and a system, which relates to the communications field, so as to resolve a prior-art problem that a receive end cannot determine a quantity of OFDMs included in an incomplete subframe, and cannot correctly receive the incomplete subframe. A specific solution is as follows: A network device determines one or more PHICH resources of a first subframe, where the one or more physical hybrid automatic repeat request indicator channel PHICH resources indicate a quantity of orthogonal frequency division multiplexing OFDM symbols included in a second subframe on an unlicensed carrier; and the network device sends the first subframe and the second subframe to user equipment. The present invention is used for information transmission.