A novel macrocyclic complex 2{[(n-Bu_2Sn)_4O_2·L_2]_2·DMF} was synthesized by the reaction of 4-(1,2- dithioethylene)methylene-3,5-disoxo-1,6-heptadiene-1,7-dis-(o-formyl)-dis-p-phenoxyacetic acid(LH_2, compound 1) with di-n-butyltin oxide. Compound 1 and complex 2 were characterized by elemental analysis, FTIR spectroscopy, and ~1H NMR spectroscopy. The crystal structure of complex 2 was determined by single crystal X-ray diffraction analysis. There are two crystallographic independent molecules in complex 2, and each molecule structure is centro-symmetric and features a central rhombus cyclic Bu_4Sn_2O_2 unit with two exocyclic Sn atoms linked at the O atoms of the four-membered ring. In molecule A, the four Sn atoms are five-coordinated. However, in molecule B, the four Sn atoms have two different coordination geometries, the endocyclic Sn atoms are five-coordinated and the exo- cyclic Sn atoms are four-coordinated. The dicarboxylate ligands in molecules A and B bridge exocylic or endocyclic tin atoms, forming two macroheterocycles with 26 atoms. Pilot studies have indicated that complex 2 has good antibacterial and antitumour activities.