The results from experimental and theoretical research of the characteristics of microwave discharge performed at a low pressure of argon-mercury mixture in a coaxial waveguide are presented. The discharge is formed and maintained due to the transformation of microwave radiation into a surface wave propagating along the boundary between plasma and dielectric. The electron density is much higher than critical density ne>>ncr (f=2.45 GHz). The radial distribution of mercury atoms emitting radiation with wavelength λ=546.1 nm was obtained. Based on numerical simulations, the spatial distributions of the electric field intensity and electron density in discharge were obtained. The experimental results are in qualitative agreement with the results of numerical simulations.