The polar growth habit of KABO crystal was discussed by the growth-units model of anionic coordination-polyhedra (ACP), and the relationship between stabilities of incorporation of those growth-units into various group faces and their corresponding morphologies was studied. It is put forward that the growth interface of crystal will be concave when negative plane is used as growth interface. Concave growth interface is very unfavorable for the quality of the crystal, because it is unsuitable for the transfer of the latent heat and impurities released during the deposition.