The effects of four low-profile additives (LPA), namely poly(vinyl acetate) (PVAc), poly(methyl methacrylate) (PMMA), thermoplastic polyurethane (PU), and polystyrene (PS), and molar ratio of styrene to polyester C=C bonds, on the mechanical properties and glass transition temperatures (T-g) for styrene-crosslinked low-shrink polyester matrices were investigated by an integrated approach of static phase characteristics-cured sample morphology-reaction conversion-properties measurements. Experimental results showed that both mechanical properties and T-g in the major continuous phase of styrene-crosslinked polyester would be generally decreased with increasing LPA content, while T-g in the minor co-continuous or dispersed phase of styrene-crosslinked polyester would show the reverse trend. Also, there usually existed an optimal molar ratio of styrene to polyester C=C bonds at MR 2/1, either below or above which would cause inferior mechanical properties and lower T-g in the major continuous phase. Based on the Takayanagi mechanical models, factors which control the mechanical properties and T,have been explored.