A method of channel assessment and channel searching in a wireless network is disclosed. The wireless network separately performs a channel assessment procedure and a channel searching procedure for channel change or another object. The channel assessment procedure is to measure a status or quality of a channel which is currently used in the wireless network. A coordinator of the wireless network designates a time interval for the channel assessment to notify other device of it. The channel assessment procedure may be performed periodically, and is preferably scheduled to allow other devices not to use the channel for the time interval which at least one device performs channel assessment.