Glass fiber reinforced unsaturated polyesters were prepared by hand lay-up technique. Effect of clay conditions and loading, as well as mixing time on tensile modulus, flammability, and wear resistance were evaluated. In general, the results showed that there might be two possible structures, dispersed and agglomerated, in the composite samples. The modulus results showed that the effect of clay drying, as well as higher filler loading increase the property. In contrast, the mixing time resulted in negative effect on modulus. The improvement on modulus and flammability might be influenced by clay dispersion due to shear and viscosity change, while the decrease on modulus and wear resistance might be caused by agglomerated structures due to lubrication effect of moisture content, and less crosslink point caused by styrene evaporation.