Abstract: The small planthopper Laodelphax striatellus Fallen (Homoptera: Delphacidae) is not only a direct pest of rice, barley and wheat etc., but also a main vector of rice stripe disease and rice black streak disease. Understanding the spatial characteristics of the insect and further developing a sampling technique to estimate its density in the winter crop fields are helpful to make decisions for controlling the planthopper and transmission of the viral diseases. Spatial distribution of the small planthopper population in barley and wheat fields in the Northern Zhejiang province was detected using the dispersal indices and Iwao regression approaches. The results showed that the planthopper populations at the stages of adult, nymph and the pooled nymphs and adults in the sampled fields tended to be in aggregative patterns of spatial distribution. Such pattern were resulted mainly from the planthoppers’ biological characteristics and environmental factors. The theoretical sampling equations were established as: , , , for the adults (n1), nymphs (n2) and adults plus nymphs (n3), respectively. According to the sampling equations, when the density of the planthopper is assumed as 5, 10 and 15 per sampling unit, 70, 40 and 20 sampling units is needed to be sampled.