The spatial distribution patterns of the aphid vectors, Myzus persicae and Rhopalosipum pseudobrassicoe, of Chinese-small-cabbage mosaic were studied based on field investigations. The results showed that nymphae and apterae aggregated through the growing season and became more aggregated with the increasing of the size of the populations, while alatae always had a random distribution. The fact that the distribution of alatae was similiar to that of diseased plants showed that alatae were the main effective vector of the disease.