Abstract: To study the electron swarm parameters in non-uniform fields, Monte Carlo simulation was used. The electron energy distribution cannot balance with the local field in a nonuniform field. There are relatively more electrons distributed in high energy range of the electron-energy distribution for the decreasing field, while less for the increasing field. The values of the mean energy, the drift veloclty and the ionization coefficients for the decreasing field are larger than the equilibrium ones, and vice versa for the lncreaslng field. The behavior of electron swarms is different depending on whether the electron moving in the decreasing field or the increasing field, resulting in the dependence of the corona inception voltage and the discharge current upon the electrode polarity in the surface discharge.