We studied horizontal velocities in different photospheric levels (115—580 km) along the active region at the onset phase of the two-ribbon solar flare on 4 September 1990 which was attended with an ejection. The photospheric matter motions with velocities from -3.5 to 2.5 km/s were detected. Both photospheric and chromospheric matter motions were mainly directed towards an observer. Some kinematic elements were revealed in the horizontal velocity structure. During the onset phase they decreased in size from 7—12 to 4—5 Мм. The velocity amplitude was decreased as well. Some twist motions were observed in the active region photosphere and chromosphere. The temporal changes of the horizontal velocities in the kernel sites and their surroundings were of a wave character and were nearly synchronous throughout the whole height of the photosphere.