When extending peer-to-peer live streaming system to IEEE 802.11-based wireless network, service guarantee for inter-domain movement is an obstacle since IEEE 802.11 has no QoS maintenance mechanism for it. The stream system must consider it itself. As a peer roams among adjacent networks, the streaming service will be interrupted by the disconnection of wireless network path and IP address changes. Here, a service guarantee mechanism is presented for the QoS of the wireless peer-to-peer living streaming while peer inter-domain roaming. A behavior prediction method based on wireless signal, a pre-caching strategy based on location, and a temp-storing strategy based on ability, are proposed to help the wireless peer rapidly resuming the topology and data transfer. The experiment results show that it can achieve good buffering for wireless roaming peers, which makes uninterrupted stream playing on mobile devices finally, when they roam among different domains.