The embodiment of the invention provides a method and device for searching for an online device in a wireless local area network. The method for searching for the online device in the wireless local area network comprises the steps that the intranet IP address, having access to the wireless local area network, of a mobile terminal is obtained; a list of candidate IP addresses located on the same network section as the intranet IP address of the mobile terminal is obtained; a connection testing data packet is sent to candidate IP addresses in the candidate IP address list by the mobile terminal, and the candidate IP address on which connection testing is successfully conducted is marked to be the IP address of the online device. By the adoption of the method and device for searching for the online device in the wireless local area network, convenient use of users is facilitated, and the efficiency of detection of non-authorized access is improved.