The invention relates to a 5-methyl-1H-tetrazole and isophthalic acid mixed ligand cobalt (II) coordination polymer magnetic material, and a preparation method and application thereof. The chemical formula of the coordination polymer magnetic material provided by the invention is {[Co7(H2O)2(mu3-OH)4(mtz)2(ip)4].13/4H2O}, wherein mtz is the 5-methyl tetrazole anion with valence of -1, and ip is the isophthalic acid anion with valence of -2. The coordination polymer magnetic material is prepared by solvothermal synthesis, and is high in productivity and good in reproducibility. The coordination polymer magnetic material is the three-dimensional cobalt (II) compound simultaneously including 5-methyl-1H-tetrazole and isophthalic acid mixed ligand, presents continuous two-step field-induced metamagnetic transition and spin-flop transition, which are from antiferromagnetic order to week spontaneous magnetization, in different external magnetic fields, and can be used as molecular-based magnetic material to have great application value in the field of material science.