The paper presents an experimental study on the relationship betweenprocess parametersand surface integrity of powder-metallurgy high-speed steel S390 in ultraprecision grinding. The optimal machining parametershave been obtained based on the Taguchi quality design method.The affected layerinduced by ultraprecision grinding has a uniform white layerand an inconspicuous dark layer; there are some carbides in the white layer of some samples; a compressive residual stress field exists on the ground surface. In addition, experiments confirm that lapping can remove the white layer effectively and increase the compressive residual stresses with a growth rate of 65%.The derived results satisfy the real requirements in practice.