Pressure assisted positioning method and device thereof are disclosed in the present invention. The pressure assisted positioning device is exerted for positioning a target under the circumstance of altitude change since the target enters a specific region. The pressure assisted positioning method includes the following steps. First, confirming the entrance of the specific region of the target and detecting a plurality of pressure data. Then, calculating a pressure variation between the two selected pressure data. At last, comparing the pressure variation to a threshold. An altitude change within the specific region is confirmed as the pressure variation is greater than the threshold. On the other hand, as the pressure variation is greater than the threshold, it refers to no altitude change within the specific region. Wherein, confirming the entrance of the specific region of the target determines via the result of detecting the target enters a region having at least a distance with a reference location of a structure with altitude change illustrated according to a map information. The pressure assisted positioning device of the present invention can not only directly detect the actual pressure data but calibrate the pressure variation information according to the pressure data and the moving statuses of the target as well. Comparing to the conventional device, the method and device of the present invention can calculate and calibrate the pressure variation information independently without any external pressure data from the barometric station.