<p>Phenolic resin presents several challenges, including low tensile strength, a high concentration of free aldehydes, and environmental pollution. This article primarily investigates the modification of phenolic resin using bisphenol A, cashew phenol, and tannic acid as substitutes for phenol to address these issues. It explores the effects of various types and quantities of modifiers on the tensile strength and other properties of sand cores. The optimal resin formulation for maximizing tensile strength is tested, and analyses are conducted on free formaldehyde content to determine the final optimal ratio. Mechanistic analysis of the modified resin is performed using infrared spectroscopy and scanning electron microscopy. Finally, the study examines the impact of the amount of microsilica powder added on the tensile strength of molding sand and analyzes its mechanism of action.</p>