The Three Gorges Reservoir with huge comprehensive benefits of flood controlling, power generation and navigation is an important project for Yangtze River. The sediment delivery rate is also an important index for the degree of intercepting sediment in a reservoir. In the view of the current research of sediment delivery ratio without consideration of the sediment from the ungauged area, at present, the result of calculation was larger than that of reality. On the basis of the measured hydrological data of the Three Gorges Reservoir area hydrological station from 2003 to 2016, the amount of sediment from ungauged area was calculated by the hydrological method. Meanwhile, the sediment delivery rates and main influencing factors were analyzed. The results were shown as follows:1) the annual average sediment yield of the ungauged area was about 1775×10⁴ t, accounting for 10.3% of the total annual average sediment yield of the Three Gorges Reservoir. In recent year, the ratio of sediment from the ungauged area has increased, and that of annual average was 26.9% from 2013 to 2016. 2)The annual sediment discharge ratio of the Three Gorges reservoir was 21.6%, and 34.1% in the cofferdam storage period, 17.0% in the initial storage period, 15.4% in the experimental water storage period. 3)Because the operation of the Three Gorges Reservoir is "store clear and discharge muddy water", the sediment delivery rate of 7-9 mouths in main flood season is generally greater than that of the dry season. But after 2013, the sediment delivery rate of main flood season is less than that of the dry season. 4)The sediment delivery ratio of the fine sediment in the reservoir was larger than the coarse sediment, and the sediment delivery ratio of the particle size d ≤ 0.062 mm, 0.062 mm0.125 mm was 23.4%, 5.5% and 11%, respectively. 5)The main affecting factor of sediment delivery rate in flood season was V/Q, but that in dry season was sediment content. When V/Q was about 170×10⁴ s, the effect of sediment delivery in the Three Gorges Reservoir was the worst. At last, the empirical formula of sediment delivery rate of the Three Gorges Reservoir was established for flood season and dry season, respectively. The result of this paper could provide reference for optimal operation of water and sediment in the Three Gorges Reservoir. The results of this paper can provide reference for optimal operation of water and sediment in the Three Gorges Reservoir.