The corona discharge phenomenon of UHVDC transmission line in high altitude area is very complicated, it is affected by line parameters, meteorological parameters, conductor surface electric field distribution and many other external factors. On one hand, the existing UHVDC transmission line electromagnetic environment parameter prediction formula is the empirical formula obtained in low altitude and standard atmospheric conditions, on the other hand, the influence of meteorological factors are ignored. Based on the massive amounts of electromagnetic environment data tested in the past six years in the National Engineering Laboratory for UHV Technology (Kunming), the big data processing method (i.e. LASSO LME method) is introduced to establish the prediction formula, which can calculate the electromagnetic environment parameter considering the comprehensive physical factors of wind speed, temperature, relative humidity and the circuit parameters of UHVDC transmission line. At last, the accuracy and applicability of the formula is verified by comparison between traditional forecasting formula and experimental data.