The dominant azimuth angle (α-angle) of telluric field rock cracks is an important parameter in geoelectric research, holding significant meaning for identifying seismic precursors. Traditional methods for calculating the α-angle based on harmonic amplitude ratios have certain limitations, particularly regarding the depiction of dynamic evolution processes and dependency on original data quality. This study aims to propose a new α-angle calculation method based on trend fitting to enhance the characterization capability of the dominant direction of rock cracks and the sensitivity of anomaly identification. This method separates the natural electric field from the telluric field, combines the phase information of various orders of electric field harmonics, and utilizes full-day data for trend fitting to calculate the dominant azimuth angle. Using observation data from 14 geoelectric stations within a 560 km radius of the 2017 Jiuzhaigou M_S7.0 earthquake epicenter (103.82°E, 33.20°N) for verification, a comparison with traditional calculation results shows that: For stations with well-developed rock cracks (Δα≤10°), such as the Pingliang and Gufeng stations, the results of the new method are similar to those of the traditional method, with minimal differences in polarization stability indicators (average SDS and MECM were 0.62% and 0.26%, respectively), verifying the correctness of the new method. More importantly, for stations exhibiting suspected pre-seismic anomalies (such as Tianshui, Chengdu, and Hanwang stations), the new method reveals anomaly phenomena, such as increased variation range or jumps in the α-angle, more significantly than the traditional method, demonstrating stronger anomaly detection capability. Therefore, the trend-fitting-based α-angle calculation method can not only effectively reflect the dominant direction of telluric field rock cracks but may also possess higher sensitivity to suspected pre-seismic anomalies, thus providing a useful supplement to pre-seismic geoelectric anomaly analysis. However, its universality across different geological environments still requires further verification.