The changing law of AC corona characteristics at different altitudes is the basis of line design in high altitude areas. This paper uses a movable small corona cage and a high-frequency current measurement system to conduct experiments at 5 altitude points within the range of 20 m~4 320 m, and collects the corona current pulse, radio interference and audible noise level data of 1mm diameter thin copper wire under different applied voltages. And through statistical analysis and fitting of the measured data, the effect of altitude on the corona current pulse characteristics and the relationship between corona current and radio interference and audible noise level at different altitudes are obtained. Studies have shown that as the altitude increases, the amplitude of the AC corona current pulse increases, and the probability distribution of the amplitude gradually disperses. The number of AC corona current pulses in a cycle increases, and the pulse formation time becomes more uniform. By the RMS of corona current regarded as an intermediate variable, the influence of altitude on the corona effect of AC lines is studied, and the RMS of corona current is linearly related to the applied voltage of the wire. And the slope k and intercept b of this linear function are both cubic functions of altitude h. The radio interference and audible noise level has a logarithmic growth relationship with the RMS of the corona current, and the functional relationship between the audible noise and the RMS of the current changes with altitude.