After different loopholes are produced by Ar+ ion-beam in p-HgCdTe, width of n-type layer has been defined by the electron beam induced current measurement. It can be observed that under the same milling condition, the width of n-type layer depends on both of the mercury vacancy concentration and the volume of the milled-HgCdTe. Further study shows that the width of n-type layer linearly decreases with an increase of the mercury vacancy concentration if volume of the milled-HgCdTe is equal. Meanwhile, the width of n-type layer will linearly increases with volume of the milled-HgCdTe increasing if the mercury vacancy concentration is kept unchanged.