The invention relates to a method for solving an internet protocol address assignment conflict and a related device and a system; wherein, the method for solving the internet protocol address assignment conflict comprises the steps of using a relay device to receive a request message used for requiring to distribute an internet protocol IP address sent by a user terminal; transmitting the request message to a dynamic host configuration protocol server; receiving a request response message sent by the dynamic host configuration protocol server, wherein, the request response message carries an IP address distributed to the user terminal by the dynamic host configuration protocol server; according to user online information, detecting whether the IP address exists an assignment conflict, if yes, ending the request response message and noticing the dynamic host configuration protocol server that the IP address is conflicting. By using the technical scheme provided by the embodiment of the invention, the IP address assignment conflict problem of a DHCP server can be solved, and accordingly, the system communication reliability is improved.