Abstract: The data combination techniques are applied on the basis of the least square method,and some details are presented: the influence of choosing common points on transformed parameters;how the transformed parameters change with the number of common points;the dissimilitude of precision between 6-parameters transformation and 7-parameters transformation.In addition,the unified self-constrained velocity field in continental China and its adjacent area and peripheral area using GPS observations from 1997 to 2005 are estimated,and the unified velocity field of this area's present-day crustal movement is obtained.