Cross-linked or linear poly-porphyrins were prepared via polycondensation of meso-tetra (4-carboxyphenyl)porphine or 4,4'-[10,20-bis(4-ethynylphenyl)porphyrin-5,15-diyl]dibenzoic acid and diamines with various chain-lengths as monomers. The relationship between the structure of poly-porphyrin with singlet oxygen yield was explored. The results indicated that when the number of carbon atoms in the flexible diamine was less than or equal to 4, the cross-linked poly-porphyrins exhibited higher singlet oxygen yield than the linear ones. On the contrary, the linear poly-porphyrins had more remarkable performance when the number of carbon atoms in the flexible diamine was larger than 4. The singlet oxygen yield of the cross-linked poly-porphyrins first increased and then decreased with the increase of the lengths of the carbon chains, while that of linear poly-porphyrins continuously increased. Moreover, the poly-porphyrins bearing the same charges on the end groups exhibited higher singlet oxygen yield. The singlet oxygen yield of the optimized poly-porphyrin was 2.37-fold that of the monomer.