Abstract: A method, device and system for determining position information are used to avoid the defects which result from the way of determining the position information of a wireless sensor node in the prior art. The method for determining the position information provided by the present invention is applied to a wireless sensor network, and includes the following steps: the current position information of a communication network node in the network is acquired; the acquired position information is determined to be the current position information of a wireless sensor node which provides service data to the communication network node.