Abstract: In this paper, the characteristics of equatorial dipole device with small dipole distance in geo-resistivity observation are studied from the two aspects of the influence coefficients and signal strength in different strata in the observation area. The results show that compared with the symmetrical quadrupole device: ① For the underlying low-resistance structure, the small dipole device is beneficial to suppress the shallow interference and obtain the lower stratum resistivity changes, ② For the underlying high resistivity structure, the ability of the small dipole device to suppress shallow interference is close to that of the symmetrical quadrupole device, but the ability to acquire resistivity changes in the lower stratum is obviously better than that of the symmetrical quadrupole device, ③ For the uniform structure, the small dipole device is obviously superior to the symmetrical quadrupole device in suppressing the shallow interference, and the ability to obtain the resistivity changes of the lower stratum is close to that of the symmetric quadrupole device, ④ The signal strength of the small dipole devices is significantly lower than that of the symmetrical quadrupole device regardless of the type of resistivity structure, however, the signal strength of the small dipole device is sufficient for observation under the technical level of the existing observation instruments.