The present invention provides a positioning method, device and system, which are applied to indoor WLAN positioning. A positioning server obtains location service information of APs in a set of APs to be measured; selects three APs to be measured in the set of APs to be measured according to a preset rule, and calculates a first coordinate of a terminal; if a calculated RSSI value of an unmeasured AP is not smaller than a difference between the measured RSSI value and a preset threshold, determines that signals of the unmeasured AP are not affected by reflection; and uses the first coordinate as a location coordinate of the terminal if all the three APs to be measured have been measured, thereby positioning the terminal.