The invention is a leather composite bactericidal mould inhibitor, and especially is the preparation of the leather composite bactericidal mould inhibitor by using quaternary ammonium salt compounds, 2-bromo-2-nitro-1,3-propanediol, iodo propynyl butylcarbamate, trilon B, a corrosion inhibitor, ethanol and water; the leather composite bactericidal mould inhibitor of the invention comprises the following components by mass: 1%-10% of quaternary ammonium salt compounds, 0.05%-3% of trilon B, 0.1-2% of 2-bromo-2-nitro-1,3-propanediol, 1%-50% of ethanol, 0.05%-5% of iodo propynyl butylcarbamate, 0.1%-20% of corrosion inhibitors, and the balance of water. The purpose of the invention is to provide the preparation of the leather composite bactericidal mould inhibitor, and the preparation comprises the following steps: mixing the quaternary ammonium salt compounds, 2-bromo-2-nitro-1,3-propanediol, and trilon B according to the mass percents with water which accounts for 50% of the balance of water, stirring for 3 hours to prepare a mixed substance A; mixing iodo propynyl butylcarbamate, the corrosion inhibitor, and ethanol according to the mass percents with the rest of water, stirring for 3 hours to prepare a mixed substance B; stirring the mixed substance A and the mixed substance B for reaction for 2 hours, allowing the mixture to stand for 2 hours, performing content determination of the mixed mixture, packaging the qualified mixture to obtain a qualified product. The purpose of the invention is also to dilute the leather composite bactericidal mould inhibitor with a dilution proportion of 50-500 times.