Abstract: An investigation on the components of the vectorial capacity of A. sinensis was carried out in Liji Commune of Peixian County, Jiangsu Province from 1979 to 1981. and the results are given as follows: 1. The average man-biting rate of A. sinensis calculated by outdoor human bait collection was 33.0, but the rate would be 11.0, one third of the former if measured by using mosquito net after 22 o'clock. The man-biting rate from July 21 to September 10 was relatively higher, forming a peak in August. 2. Observation on blood digestion and ovary development and on the freshly blood-engorged females of A. sinensis put into vials separately for ovipositipn suggested that an average of 2.5 days was needed to complete a gonotrophic cycle, and for the first gonotrophic cycle after emergence about 3.5 days were needed. 3. A total of 11,186 inosquitos of A. sinensis have been dissected within the three years, the parous rates being 0.581-0.621, and the daily survival rate 0.856-0.873. 4. 3,755 specimens of blood meal of A. sinensis were collected from human dwellings and cattle sheds at the daytime, making the ratio of human blood-fed 17.1%; 1,273 specimens were from the bean field, the ratio of human blood-fed 2.6%. Adjusting the result with different resting places and host preference, the human blood index of A. sinensis estimated in this area was 0.104.