Embodiments of the present invention provide a method and apparatus for receiving fragments as well as a method and apparatus for transmitting fragments. The method for receiving fragments includes: receiving a group of fragments from a transmitter through a first channel, where the transmitter suspend transmitting a next group of fragments after the group of fragments is transmitted; and transmitting one or a plurality of first acknowledgement messages to the transmitter through the first channel immediately after the group of fragments are received. According to embodiments of the present invention, the acknowledgement messages may be immediately transmitted to the transmitter through a current channel after one group of fragments are received through the current channel, thereby avoiding the delay of a fragment receiving and transmitting process, which is caused by the competition and occupation of the channel by other nodes, and thus improving transmission efficiency.