In this work, the effective parameters in liquid polysulfide curing system were optimized by D-optimal design method. Five main components in the formulation, carbon black, vulcanizing agents (MnO(2), Na(2)Cr(2)O(7), and PbO(2)), CaCO(3), fumed silica, and chlorinated paraffin, were selected. Mechanical and chemical properties of the samples were investigated. The results showed that tensile strength, hardness, viscosity, and optimum cure time (t(90)) presented a suitable coordination with reduced quadratic model. For elongation at break and swelling tests, reduced two-factor interaction (2FI), and for peel strength, a linear model showed the best correlation. To achieve the desirable properties for liquid polysulfide sealants used in fuel tanks, an optimized amount of the above components in the formulation were used. Finally, MnO(2) curing system, compared with Na(2)Cr(2)O(7) and PbO(2), was selected as the best choice. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 2550-2562, 2011