The article is concerned with the modification of lipase with Tween-80. We can use formaldehyde or glutaraldehyde to connect Tween-80 and lipase covalently. Comparing the difference between modified lipase and nature lipase, we can get some conclusion. The results are follows: with the same concentration of formaldehyde and glutaraldehyde, the activity of lipase modified by formaldehyde is higher than lipase which was modified by glutaraldehyde; while the lipase modified by glutaraldehyde has higher connecting efficiency than lipase modified by formaldehyde. With the different concentration of formaldehyde, the modified lipase has the highest activity when the concentration of formaldehyde is 1. 25 mg · mL-1. When the pH of phosphate is higher than 7, the modified lipase has higher activity; when the pH of phosphate is lower than 7, the nature lipase has higher activity.