To investigate the deterioration of fats and oils by hot plate heating, several experiments were carrid out. Lard (2g, 10g) and /or vegetable oils (2g, 10g) kept in beaker (500mL) were heated using hot plate for 10min at 200°C. Lard and vegetable oils with or without silicone oil (5 ppm) were also heated using the same way. The effect of some antioxidants such as tocopherol, silicone oil and lecithin on the thermal deterioration was compared. To prevent the deterioration of lard during heating, adding a mixture of tocopherol (0.1%), soybean lecithin (0.5%) and silicone oil (5ppm) showed better effect than adding them separately. Addition of silicone oil (5ppm) alone could supperss the deterioration of fats and oils by heating, residual tocopherol increased. Silicone oil effectively suppress the thermal deterioration, but no such effect was noticed on autoxidation of oils. Commercially available cooking oils with lecithin showed preventive effect on deterioration of oils by heating. The degree of thermal decomposition of tocopherol in heated oils at 200°C was found to much more high levels of oleic acid in sufflower oil (HOSO) than high levels of linoleic acid in safflower oil (HLSO). Deterioration of oils was affected remarkably to the specific surface area and heating temperature.