The article describes preparation of vinyl ester resin & diluents effect on the mechanical properties of glass fiber-reinforced composites. Resin is prepared by reacting epoxy LY-556 with methacrylic acid in presence of catalyst & thermal polymerization inhibitor. Progress of reaction was monitored by measuring the acid valve of the reaction. VM and VB resin mixture were prepared by mixing the vinyl ester resin with butyl methacrylate and methyl methacrylate in 10: 4 molar ratios respectively using benzoyl peroxide as a initiator (4phr) at 300C till mixture become homogenous. With the use of these resin mixtures two laminate sheets were fabricated using a glass fiber in compression molding machine. Resin content and degradation temperature of the both laminates were studied using TGA. Mechanical, thermal test were performed on both composite laminate to study the effect of diluents on the properties of composite laminates followed by the morphological study of tensile fractured surface of samples by using scanning electron microscopy. A significant increase in the number of methylene groups and polar nature of groups in the diluents present in vinyl ester resin (i.e., increasing the bridge length) did not show any major significant effect on flexural strength & inter laminar shear strength but tensile strength, increased.