&Solar Physics BRussian Ksolar flare// Line-of-sight (LOS) velocities on chromospheric and photospheric levels in the H_α-loops are studied in the course of the flare 1b/M2.2 development on 3 September 1990. The spectra and filtergrams were derived with the solar telescope ATsU-26 at the Terskol Peak Observatory. Temporal variations of LOS velocities at loop tops and bases were compared with H_α- and HXR-fluctuations. Quasiperiodic variations of H_α- and HXR-intensities and velocity with periods of about 3 min at upper levels and of about 1-2 min in the photosphere took place. XR time-profile and H_α-filtergrams show that elementary XR spikes are connected with consecutive disturbances of the H_α-loops in arcade. H_α-intensity and velocity at the flare bases are much greater than at their tops (the analogous picture was observed by Yohkoh in SXR-loops). At the photospheric levels, material lifting in loop bases was recorded only when the H_α- and HXR-intensities were at minima. The intencity maxima were accompanied by descending motions of photospheric plasma. Different mechanisms may be efficient at early stages of elementary XR spikes and at their maxima. This is a reason of observed peculiarities of velocity field in the chromosphere and photosphere.