Passive source location attracts a growing interest due to its usefulness in various applications such as wireless communications, microphone arrays, sensor networks and so on. This paper combines the time differences of arrival (TDOA) and gain ratios of arrival (GROA) techniques to present a novel dual-station source location method of a known altitude object in 3D space. The closed form solution and performance evaluation are also given in the following section. The final simulation shows that the proposed method is feasible when the constraint height error is small and can reach the CRLB. GDOP analysis shows that the error is large on the midperpendicular line of the two stations.