The factors influencing lead button mass in the lead fire assay method were thoroughly investigated.Experiments were conducted to analyze the specific effects of effective sulfur, fixed carbon content, type and dosage offlour, and potassium nitrate addition on lead button mass. Results indicate that lead button mass primarily depends onthe effective sulfur and fixed carbon content in the sample. Under a sample weight of 15 g, for every 1 % increase ineffective sulfur, the lead button mass increases by approximately 3.2 g; for every 1 % increase in fixed carbon, the massincreases by about 4.6 g. When flour and potassium nitrate are used to control lead button mass, for every 1 g increasein flour, the lead button mass increases by approximately 11.6 g; for every 1 g increase in potassium nitrate, the massdecreases by about 3.6 g. Based on the experimental results, a formula for calculating reducing power is derived, andthe lead button ingredient composition is optimized. Verification experiments show that the optimized ingredientscheme can control lead button mass within 20-40 g, with the success rate of the first assay increasing to over 90 %.Applying this optimized scheme in daily testing improves the qualified rate of lead button mass from 76.7 % to 95.3 %,significantly enhancing testing efficiency and accuracy.