The embodiments disclose a method for scanning in a radio communication system, in particular in a WLAN (Wireless Local Area Network), including transmitting by a MS on all channels a probe message containing the IP address of the original AP of the MS and an MAC address of the MS; switching to the original channel; transmitting a response inquiry message to the original AP; and receiving a probe response message within a predetermined period, wherein, if the AP of the probe message received on the channel is not the original AP, then the AP transmits the probe response message containing the MAC address to the original AP according to the IP address; and the original AP buffers the probe response message received, and transmits the probe response message to the MS according to the MAC address after the response inquiry message sent by the MS has been received. The embodiments further disclose a scanning system in a WLAN. By using the method and system, not only the time delay during the scanning is reduced, but also the network security is improved and the difficulty for realization is decreased.