Abstract:The Chinese rice grasshopper (CRG, Oxya chinensis) occurs one generation a year in Zhejiang Province, it mainly damages on early rice and early planting single late rice in the middle and lower reaches of Yangzi River Valley. There were close relationships among population densities of CRG (at tillering, ear bearing-early heading stages) and damaged leaf rate, leaf injury index, and yield loss rate of rice; the harmfulness and yield loss rate of rice increased with the population of CRG. After the damage of CRG, the intensity of photosynthesis of rice plant was weakened, its young panicle differentiation was abnormal, grain setting rate decreased, blighted grain number increased, and grain weight reduced, all of these were main causing factors of rice yield reduction. The simulation injury test showed that the rice plant at tillering stage has rather strong compensation ability against the damage of CRG, and then the yield loss increased with the delaying of injury test stage. The tolerable rice yield loss level was determined as 2.5% -3.0%, the suitable stage of CRG for spraying were 2nd-3rd instar nymphs, the action thresholds at tillering and ear bearing-early heading stages were 10 and 5 nymphs per square meter res- pectively. Fipronil and triazophos were recommended as the desirable insecticides for CRG control.