The invention discloses a biological compound preparation for improving yield and quality of the tobacco leaf at the upper part of tobacco. The biological compound preparation mainly comprises the following components in parts by weight: 25-35 parts of zinc sulfate heptahydrate, 15-25 parts of magnesium sulfate heptahydrate, 5-10 parts of boric acid, 10-20 parts of potassium citrate and 5-10 parts of potassium nitrate. The biological compound preparation additionally contains selenium dioxide, humic acid, sodium dodecylbenzenesulfonate, epibrassinolide and the like. As the biological compound preparation is prepared by adopting the formula, by timely spraying the biological compound preparation on the leaf surface after tobacco topping, the increase in the upper leaf area can be significantly promoted, the width of leaf blades can be particularly increased, the organizational structure of the upper leaf is optimized, the decrease in nicotine content in the tobacco leaf is promoted, the potassium content is greatly increased, the leaf blades further become thin and are easy to be baked, the quality and appearance quality of the tobacco leaf are improved, and the industrial application value is further improved.