The normal operation of the high-voltage transmission lines is seriously affected by the instability of the slope of the transmission line pole tower base. Taking the typical tower foundation soil of two high voltage transmission line towers in Guangdong as the research object, the sensitivity analysis of the influencing factors of tower foundation slope stability based on an orthogonal test was carried out by combining indoor experiment, theoretical analysis, and numerical simulation. The results show that 882^# soil has greater cohesion than 902^# soil, but the internal friction angle is smaller. The ExpDec2 mathematical model and ExpAssoc mathematical model can better simulate the soil-water characteristic curve of 882^# soil and 902^# soil. The range analysis of 4 factors and 4 horizontal orthogonal tests showed that slope height had the greatest influence on the stability of 882^# soil slope, and slope angle had the greatest influence on the stability of 902^# soil slope. This study shows that the main influencing factors of slope stability of two different soils in Guangdong are quite different, and they should be treated differently in the construction and operation of high-voltage transmission line tower projects.