The expansion of enterp rise scale boundary is an i mportantmethod for an enterp rise to realize gr owth and its essence is to construct and cons olidate the radius of enter p rise capacity . From the angle of core competence, this paper analyzes the main fact ors which determine the radius of core enter p rise competence, indicates that the change of enterp rise scale boundary is regular within the radius of different core capacity and that capability radius of an enterp rise deter mines the upper limit of scale boundary while the core competence radius of an enterp rise determines the lower li mit of scale boundary .