Three thiophene-based conjugated microporous polymers (CMPs: TTPTh, DBTh, and TBTh) were prepared by Sonogashira–Hagihara cross-coupling polymerization, and their structures were characterized by FTIR, ss ¹³C NMR, and elemental analyses. The obtained TTPTh, DBTh, and TBTh have excellent thermal stability with decomposition temperatures of 615, 298, and 290 °C and high porosity with BET surface areas of 564.97, 416.99, and 521.30 m² g⁻¹, respectively. The results reveal that the conjugation of the CMPs plays an essential role in determining the fluorescence sensing performance. Because of the perfect conjugation arising from a low volume of the building block or low degree of cross-linking, DBTh has high fluorescence sensing sensitivity to 2,4-dinitrophenol (DNP) and iodine with K_sv values of 5.76 × 10⁴ and 4.52 × 10⁴ L mol⁻¹ and LODs of 1.56 × 10⁻¹⁰ and 3.32 × 10⁻¹² mol L⁻¹, respectively. To the best of our knowledge, the sensitivity to DNP and iodine of DBTh is the highest among all thiophene-based CMPs reported to date. Our study provides an essential understanding for the structure design of fluorescent sensors of CMPs.