The unmanned driving of industrial trains are key links in the upgrading of traditional industries. However, the industry lacks positioning technology that fulfills the requirements of high reliability, high precision, and low maintenance in the face of harsh environments, such as high temperature, dust, and metal interference. SAW RFID technology has the characteristics of wireless passivity, high-temperature resistance, and resistance to harsh environments. This paper proposes a positioning method based on dual-antenna time-delay difference. Compared with single antenna ranging positioning, the proposed positioning method offsets the influence of environmental temperature and improves positioning accuracy and reliability. A time-delay measurement method based on fractional Fourier transform was studied. Simulation and experimental results show that the delay measurement error can be reduced to one-third of that of the matched filtering method, with an accuracy of 0.35 ns. The experiment based on the built platform showed a positioning accuracy of 6.2 cm, and the error was reduced to 3.48 cm in a shorter interval. Finally, the system was preliminarily applied in a steel plant.