In this paper, treatment of 1,1'-(1,4-butanediyl) bis-1H-benzotriazole (bbbt) and KSCN with Co(Ⅱ), Mn(Ⅱ), or Cd(Ⅱ) afforded three two-dimensional rhombohedral grid coordination polymers [M(bbbt)2(NCS)2]n (M ) Co, 1; Mn, 2; Cd, 3). The two-dimensional rhombohedral grids are parallel to the crystallographic ac plane. The rhombohedral grid consists of 44-membered rings of M4(bbbt)4, and gives the dimensions of 12.913×10.764 Å for polymer 1, 13.106×10.797 Å for polymer 2, and 13.256×10.870 Å for polymer 3. The three polymers' third-order nonlinear optical (NLO) properties were determined by Z-scan technique in DMF solution. The results show that all three polymers show very large NLO absorption and strong NLO refraction properties. The third-order NLO absorptive coefficients R2 are 5.4×10-9m W-1 for polymer 1, 5.2×10-9m W-1 for polymer 2, and 5.0×10-9m W-1 for polymer 3. The R2 values are larger than those of all the reported cluster compounds. The NLO refractive index values n2 of the three polymers are 5.73×10-19, 3.55×10-19, and 3.07×10-19 m2 W-1, respectively. Their hyperpolarizability γ values are calculated to be 2.40×10-30 esu for polymer 1, 1.52×10-30 esu for polymer 2, and 1.50×10-30 esu for polymer 3. The γ values are comparable to those of clusters and better than those of organometallic compounds, semiconductors, and fullerene.