A sensitivity analysis based on Monte Carlo was performed on frequency electromagnetic fields (FEF) to evaluate relative importance of parameters. Charge simulation method and law of Biot-Savart method were used to establish calculation model of FEF intensity. Sensitivity results distinguished the height of transmission line, interphase spacing, split number, split spacing, sub conductor radius as influential factors, while the height ranked the top, followed by interphase spacing, split number and split spacing were not conspicuous as the first two, sub conductor radius and others were identified as negligible factor to power frequency electronic fields (PFEF) intensity. Meanwhile, the height of transmission line and current were recognized as factors to affect power frequency magnetic field (PFMF), the contribution of height to intensity is proved to be more significant compared with the current. This study provides some useful findings to electromagnetic environment research and high voltage transmission line design