Abstract: A new approach to design new pesticides was introduced.It was based on the data that in some cases oligosaccharide molecules in cluster form display much higher bioactivity than the corresponding oligosaccharide molecules.That was called "cluster effect".The activities of some polymers of medicine that was significantly enhanced by their "multivalent" or "cluster effects" were inumerated.It was anticipated that the mechanism of cluster effect could be used to screen and create highly active pesticides.