[en] LiPb loop is the indispensable facility to investigate key issues for liquid LiPb blanket of fusion reactors, and its distribution of temperature and velocity fields of liquid LiPb is very necessary for the analysis of experiment results. DRAGON-I is the first thermal convection LiPb loop of China, the temperature and velocity fields of liquid LiPb was simulated with 2D and 3D models by FLUENT code. The results show that the temperature of liquid LiPb changes in conformity with design demands, with less change on the section of pipe diameter direction, and there was almost no fluctuation for velocity inside the pipe except for small regions at the two right-angle corners at the top of the loop, the velocity is averaged about 0.14 m/s. (authors)