In order to study the effect of attitude for corona inception voltage of AC transmission lines conductors in the altitude areas ranging from 0 to 3000 meters, conducted a series of tests about the corona characteristics of AC six-bundle conductors based on the mobile corona cage at Wuhan, Xining and Haibei respectively. Recorded the number of photons after conductors corona discharge by ultraviolet imaging detector. Conductor corona inception voltages were acquired by the tangent method. The measurement result shows that conductors corona inception voltage decrease with increasing altitude. Corona inception voltage is reduced about 8.12% if altitude rises 1000m. The exponential and linear correction equations suitable for 6 × LGJ-400/50 conductors are introduced. The maximum tolerance is less than 5% and meets the engineering needs.