The measurements of the plasma velocity in the SMOLA helical mirror by observation of the Doppler shift of the Hα spectral lines emission were done by high spatial resolution spectrometer. A set of experiments was carried out with the different configuration and amplitude of the magnetic field. Potential is driven by plasma gun potentials. The radial distribution of the Doppler shift of the Hα line is used to calculate the velocity of neutral hydrogen, which gives the estimate of the plasma rotation velocity ω ≈ 10 6 s -1 . The indicated velocity corresponds to the presence of the radial electric field E ~ 70V/cm. The dependence of the plasma rotation velocity on the radial profile of the electrostatic potential is discussed.