Two complexes, [Hg2(L1)2Br4]·4DMF·2H2O (1) and [Hg4(L2)4Br8]·8DMF·2H2O (2), have been synthesized and characterized from two flexible bis(pyridylurea) ligands (L1 and L2) with mercury(II) bromide respectively. Both the two complexes exist as centrosymmetric metallamacrocycles with four-coordination Hg(II) centers, but they present different architectures with slightly adjusted 3- and 4-position of nitrogen atom in the pyridyl rings from the two ligands. Complex 1 exists as a [2+2] metallamacrocycle with L1 as bidentate ligands bridging two HgBr2, while complex 2 exists as a novel 84-membered [4+4] metallamacrocycle, which indicates that the nature of the ligand plays an important role in the coordination networks.