  We develop a theory to compute the domain-wall magnetoresistance (DWMR) in
antiferromagnetic (AFM) metals with different spin structures. In the diffusive
transport regime, the DWMR can be either {\it negative} or positive depending
on the domain-wall orientation and spin structure. In contrast, when the
transport is in the ballistic regime, the DWMR is always positive, and the
magnitude depends on the width and orientation of the domain wall. Our results
pave the way of using electrical measurements for probing the internal spin
structure in antiferromagnetic metals.
