Abstract: A kind of potassium fertilizer based lignin was made from modified lignin and potassium chloride, leaching experiment and pot experiment were conducted to test the effect of modified lignin on slow-releasing potassium fertilizer and the Bio-utilization. The results showed that lignin could not only reduce the loss of potassium fertilizer but also promote the growth of tomato and maize, and increased uptake of potassium by crops. Lignin from paper-making waste liquor was used as slow-releasing material to potassium fertilizer, which was propitious to resources utilization and environmental protection.