In order to find out the vertical distribution characteristics of water temperature in Xiluodu Reservoir during ecological regulation period under the condition of inflow change, a two-dimensional water temperature model of Xiluodu Reservoir was established based on the measured topographic and hydrological data using the research methods of on-site water temperature monitoring and CE-QUAL-W2 water temperature numerical simulation. The dynamic change process of water temperature of the reservoir from January 15 to April 30, 2021 was simulated, and the two-dimensional water temperature distribution law of the reservoir area and the influence of different outlet elevations on the discharge water temperature during the ecological regulation period (March to April) were emphatically analyzed. Results showed that the temperature difference between the surface and bottom water in front of the dam of Xiluodu Reservoir occurred in mid-March, which reached 2.02 ℃ in late March, and the vertical temperature gradient was within 0.10 ℃/m. In April, the maximum vertical temperature difference grew even larger, which reached 2.41 ℃ in early April and 2.81 ℃ in late April, and the vertical temperature gradient was within 0.15 ℃/m. By comparing the two operating conditions of no stacked beam door and one stacked beam door, it was concluded that the average discharge water temperature of the reservoir increased by 0.13 ℃ when the stacked beam door was in operation. The research results can provide some technical support for the follow-up experiments of water temperature ecological regulation of Xiluodu Reservoir.