An RRU channel frequency response difference obtaining method, device, and system are provided. In the method, multiple RRU channel groups are obtained between a BBU and an RRU, and all RRU channels in each RRU channel group are interconnected by using a same bridge. The method includes: separately obtaining, for a first RRU channel and a second RRU channel that are interconnected in any RRU channel group, a first frequency response difference between the first RRU channel and a separate RRU channel and a second frequency response difference between the second RRU channel and the separate RRU channel, where the separate RRU channel is not in the any RRU channel group; and obtaining a frequency response difference between the first RRU channel and the second RRU channel according to the first frequency response difference and the second frequency response difference.