Glucosidase is an important digestive enzyme in insect. The plant-sucking insect, the whitebacked planthopper Sogatella furcifera, ingests rice phloem sap and must use this enzyme to decompose the main sugar source of disaccharide sucrose into monosaccharide glucose and fructose for normal absorption. In studying the resistant mechanism, we investigated the changes of glycosides activity and insect body weight of S. furcifera after fed on the highly-resistant rice variety Rathu Heenati (RHT) and susceptible TN1 The 4-, 6-and 8-week old rice plants of RHT and TN1 were enclosed with mylar cages. The brachypters were introduced into cages and collected at 3 days after infestation and weighed. The uncaged insect served as control. Insects were homogenized with citrate buffer and centrifuged. Homogenates and substrate (p-nitrophenyl-a-glucoside) solution were incubated at 33℃ for 2 b and added with Tris-HCl buffer for interruption enzymatic reaction. The absorbance of color solutions was measured at 420 nm. The plant-sucking insect, the whitebacked planthopper Sogatella furcifera, ingests rice phloem sap and must use this enzyme to decompose the main sugar source of disaccharide sucrose into monosaccharide glucose and fructose for normal absorption. In studying the resistant mechanism, we investigated the changes of glycosides activity and insect body weight of S. furcifera after fed on the highly-resistant rice variety Rathu Heenati (RHT) and susceptible TN1 The 4-, 6- and 8-week old rice plants of The brachypters were introduced into cages and collected at 3 days after infestation and weighed. The uncaged insect served as control. Insects were homogenized with citrate buffer and centrifuged. Homogenates and substrate (p-nitrophenyl-a -glucoside) solution were incubated at 33 ° C for 2 b and added with Tris-HCl buffer for interruption enzymatic reaction. The absorbance of color solutions was measured at 420 nm.