A2MnIIMn2III(SeO3)6　(A　=　Sr　and　Ba)　are　found　to　have　a　monoclinic　space　group　P21/c,　where　Mn3+　ions　form　a　distorted　honeycomb　lattice　centred　by　the　Mn2+　ions.　The　samples　of　two　isostructural　compounds　were　syn-thesized　using　a　conventional　hydrothermal　method　and　characterized　by　many　methods　including　EDS,　XRD,　FT-IR,　UV-vis　diffuse　reflectance　spectra　and　thermal　analysis.　Magnetic　measurements　confirm　that　two　com-pounds　display　a　similar　magnetic　behavior　with　a　short-range　and　a　long-range　antiferromagnetic　order　at　low　temperature,　while　the　metamagnetic　transition　can　be　observed　under　applied　magnetic　field.　In　addition,　the　spin-frustration　effects　of　two　compounds　are　also　investigated.