The molecular field treatment of the properties of magnetically dilute antiferroagnetic crystals are given. The syste is composed of two kinds of magnetic ions or same kinds of magnetic ions with dfferent environm ent and is arranged antiferromagnetically along a direction alternately in low temperature. Each kinds of antiferromagnetic lattices are again divided into oppositely directed-sublattices. Transitions from ordered antiferromagnetic ground state to paramagnetic state is studied. Susceptibility versus temperature curve above the Neel point is like that of ferrimagnetics. Specific heat discontinuity are compared with Onsager's result.