The development of fiber optic pressure sensor applied to the weigh in motion (WIM) field is discussed from a practical viewpoint in this paper. The research of fiber optic pressure sensor based on intensity modulation, wavelength modulation, and phase modulation is introduced respectively. The principles, structures, advantage and disadvantage are also described for these sensors. By comparing the characteristics of various fiber optic pressure sensors, it has been found that the wavelength modulated fiber optic pressure sensor would become a mainstream of research for WIM.