Abstract: In order to improve the rotating accuracy of main shafts and optimize the structure of bearings in grinding machines, Hangzhou Machine Tool Plant has won initial success by substituting oil-impregnated bearings, which were preloaded elastic deforming, for hydrodynamic bearings.The new bearings have been tested by trial running for more fhan 300 hours, a friction coefficient of 0.02-0.05 and a temperature rising of about 200℃ were measured These data are in the range of hydrodynamic bearings and iron base oilless bearings.The were value is about 10μm and the starting torgue of main shafts is twice as large as that of hydrodynamic bearings. Experiments also showed that full supply of oil and controlling of grinding force within rating limit are two important conditions for the normal running of elastic deformation oil-impregnated bearings.