A method for automatically allocating channels of a wireless network system comprises the steps of: actuating one of access points (APs) for collecting channel status information, such as channel numerals and Received Signal Strength Incident (RSSI), of the other of the access points near by that access point; calculating an accumulated RSSI value of each of the access points according to the collected channel numerals and the RSSI value via a Network Management Server (NMS); calculating the accumulated RSSI value of each of the access points by weighting to obtain a weighted RSSI value thereof; and switching an operation channel of the actuated access point into the better channel having a relatively lower weighted RSSI value for improving the overall efficiency of the wireless network system. Furthermore, the method for automatically allocating channels can be used to periodically monitor the channel status of the channel corresponding to each of the access points, so as to actively fine-adjust the channel of that access point or to change a monitor period.