Two Hg2+ probes (Tpy1 and Tpy2) with D-π-A structures were designed and synthesized by introducing 9-hexyl-9H-carbazole and triphenylamine units to 4'-(4-phenyl)-2,2',6',2''-terpyridine component respectively via Suzuki coupling reactions. Their structures were characterized by melting point, 1H NMR, 13C NMR, mass spectrometry and elemental analyses. Compared to other metal cations, the target probes Tpy1 and Tpy2 have good selectivity for Hg2+. The Hg2+ can be identified efficiently in solution by UV-vis absorption spectrophotometry or naked eye observation under ultraviolet lamp. DFT calculations indicate that when the probe is chelated with Hg2+, the intramolecular charge transfer (ICT) effect is significantly enhanced, and the absorption spectra are red shifted accordingly. In addition, different electron donating groups attached to the probe molecules can influence the recognition of Hg2+ significantly. The detection limits are 2.51×10-6 mol/L for Tpy1 and 4.40×10-6 mol/L for Tpy2 respectively. When the triphenylamine group was attached on the probe structure in Tpy2, the probe can not only detect Hg2+, but also exhibit response to Cu2+ cations.