Abstract: Studies were undertaken in 32 Oncomelania Snail-infected canal sections in Lumu Commune of Wuxian County in 1980. The results showed that the snail density in each canal section determined in the first survey was parallel to the total population of that section. There was a linear positive correlation between the snail density detected in the first survey and the density of the total snail population. However in low snail popular tion (below 0.7/square Chinese foot) area, snails may not be detected in the first survey. Results also showed that a linear positive correlation existed between the density of the snail eggs and the density of the total snail population.