Corona cage six bundle conductors corona loss were measured, and corona onset electric field was obtained. The IEC 61284 standard was adopted as altitude correction. And add to this, exponential form and linear form altitude correction formulae were adduced. The results show that, exponential form altitude correction formulae calibration error and dispersion are less, and the adjustment effect is better; for convenient engineering application, linear correction formulae can be adopted; for estimation in the rough, sea level as base, as altitude increases every 1000m, conductor corona onset electric field decreases about 7%.