The interactions between octasulfonato-octakis (dodecyloxy) calix[8] arene and pyrene in aqueous solutions were investigated by fluorescence spectroscopy. In water, pyrene was incorporated in the hydrophobic domain of this calixarene forming inclusion complex. The association constant for 1:1 complex is 5.0×10^6mol^-^1.dm^3. Compared with the interactions between octasulfonato-octakis (butyloxy) calixarene or octasulfonato-octakis (hexyloxy) calixarene and pyrene, the much longer hydrocarbon chains of our host lead to obvious enhancement on the apolarity of the cavity but no obvious increase in the association constant. Besides, the salt effect of NaCl and co-solvent effect of methanol on this interaction were also investigated. NaCl makes no obvious influence when its concentration is below 0.01mol.dm^-^3. Methanol also causes no obvious influence when its volume concentration in water is lower than 10%, but gives an obvious decrease in the association constant when its concentration is higher than 20%.

Key words: CALIXARENE, ETHER, PYRENE, INTERACTIONS, SOLVENT EFFECT, SALT EFFECT