In order to understand the effect of the surface evaporation on thermocapillary convection in an annular pool, a series of numerical simulations on thermocapillary convection of cold water around 4℃ in the pure steam environment were carried out. The results show that the surface evaporation mass flux is mutually coupled with thermocapillary convection. With the increase of the evaporation Biot number, the surface temperature is dropped, and the evaporation mass flux near the hot wall is increased, but it near the cold wall is closely related to the Marangoni number. When the Marangoni number is small, the dimensionless total evaporation mass at the evaporation interface increases with the increase of the evaporation Biot number; while when the Marangoni number is large, the total evaporation mass increases first and then decreases with the increase of the evaporation Biot number. With the increase of the aspect ratio and the radius ratio, the flow strengthens and the total evaporation quality also increases.