Spiro-oxindoles were prepared efficiently via multicomponent reactions (MCRs) for finding the new chemosensors. Also, the use of the efficient nanocatalysts based on SBA-15 in these reactions are so important. Therefore, the functionalization of SBA-15 by different organic compounds are common to produce new efficient nanocatalysts. Herein, SBA-Pr-N-Is-Bu-SO3H as an efficient nanoporous catalyst was applied in the synthesis of (5,6,7,8-tetrahydro-chromene)-4,3′-spirocyclic oxindoles through the three-component reaction of isatin derivatives, malononitrile and dimedone under reflux conditions in high yield and short reaction time. Among all spiro-oxindole derivatives, 2-amino-7,7-dimethyl-5′-nitro-2′,5-dioxo-5,6,7,8-tetrahydro-spiro[chromen-4,3′-indoline]-3-carbonitrile was investigated in fluoresence spectroscopy. According to the obtained results it was observed that in the presence of various cations such as, K+, Ca2+, Na+, Cu2+, Zn2+, Cr3+, Fe3+, Fe2+, Mn2+, Co2+, Al3+, Pb2+, Ag+, Cd2+, Ni2+, Hg2+ and Mg2+, it can selectively detect Hg2+ ion and increase the emission intensity. Its calculated detection limit was 4.6 × 10−7 M, which can be considered a good value. Also, in order to determine the stoichiometric ration for ligand and Hg2+ ion, Job's plot test was performed and the ratio was 1:2.