We used GPS method to investigate the preseismic, coseismic and postseismic deformation due to the 27 September 2003, Mw = 7.3 Chuya (Altay) earthquake, which occurred south of Russian Altay mountains in southern Siberia near the Russia-Mongolia-China border. On the basis of GPS data measured during the campaigns of observation covering the period 2000-2007, we determined the magnitude and space distribution of 3D displacement fields for different epochs. Geodynamical GPS network consists of 23 sites and extends over structural elements of Russian Altay and surroundings territory (from 49.5°N to 54.8°N, from 81.2°E to 91.4°E). GPS data have been analyzed by GAMIT-GLOBK. Evidence was available of the existence of preseismic (2000-2003 years), coseismic (2003-2004 years) and postseismic (20042007 years) processes in this region. We used absolute gravity observation to check vertical motion at base points. Map of preseismic contemporary rates showed values from 0.5 to 10 mm/y and features in 3D velocity field. Russian Altay preseismic motion is connected with present-day displacement in West China and Mongolia. By analysis of the GPS data for 20032004 we got the map of coseismic displacements, reflecting the right-lateral strike-slip process in epicentral zone (130N140N orientation for rupture line). Coseismic horizontal displacements depend on distance between rupture line and GPS benchmarks position, for example, we obtained values from 350 mm at 15 km to 25 mm at 90 km. Vertical motion was smaller (10 ÷ 40 mm). GPS data for 6 benchmarks in epicenter zone show correlation with 2-D model with parameters for jump on rupture line – 2 m, for maximal depth – 15 km, for shear strain 4 MPa. 3D modeling of coseismic process allowed us to understand displacement field for vertical motion at the end of earthquake rupture (10  40 mm jump). Coseismic deformation on 10 level extended over the epicentral zone (100 km). Postseismic displacement field (2004-2007 years) showed the right-lateral motion in epicenter zone (3 ÷ 7 mm/y). Postseismic data allowed to develop a postseismic model for Chuya earthquake and to determine lower crust parameters (viscosity 10 Pas). Analyses of 2000-2007 data allowed us to separate ongoing seismic motion from tectonic motion for West part of Russian Altay (2 mm/y to NW).