Recently, a distributed fiber optic sensor named phase optical time domain reflectometer or phase-sensitive optical time domain reflectometer (Φ-OTDR) has been used in the localization and monitoring of earthquake waves, underwater facilities, etc. Precision in the localization of external perturbations on the fiber is crucial for effective problem resolution. The conversion coefficient between the extracted phase signal detected by Φ-OTDR and the corresponding perturbation signal acting on the fiber significantly impacts localization accuracy. Therefore, the characteristic of parameters relative to the conversion coefficient in Φ-OTDR should be deeply researched. Then, based on the established mathematical model of coherent Φ-OTDR, modulus, statistical phase, phase change, and peak difference of coherent Φ-OTDR with and without the static region is analyzed, respectively. The analysis reveals that when coherent φ-OTDR has perturbations homogeneously distributed along the fiber, there is no static region on the phase change-fiber length plane. At this point, although the waveform like the information of external perturbation still can be found in the retrieved phase change in the direction of pulse sequence, the phase change does not have a strictly linear relationship along the fiber. It is different from what was expected in coherent Φ-OTDR having the static region, which means that coherent Φ-OTDR must have the static region if a higher localization accuracy is needed. A localization case demonstrates that the proposed method with the designed static region enhances localization resolution by 210% compared to the traditional coherent φ-OTDR without the static region. These findings underscore the importance of the conversion coefficient and the relevance of the static region in Φ-OTDR for achieving accurate and effective localization.