In recent years, lost foam technology has rapidly developed in China due to its advantages such as low pollution, flexible processing, low labor intensity and good repeatability, showing significant advantages over other casting processes especially in the production of box and shell products. In this paper, defects such as burning-on, porosity and sand wash that are prone to occur in products such as flywheel housing during the lost foam casting process were analysed. By adjusting the combination process method of the pattern, optimizing the product pouring system, arranging the exhaust and slag discharge risers, and ensuring the rationality of the layout of the inner gate inlet, measures to solve the casting defects of related products are proposed based on the production situation. After the production and machining process, the goal of solving casting defects in the product is achieved.