Thermal performance of a trapezoidal solar pond is numerically simulated by a two-dimensional unsteady model based on the large eddy simulation method. The temperature distributions of the Reynolds Averaged Navier-Stokes (RANS) and the Large Eddy Simulation (LES) are contrasted against the experimental data to verify the validation of the simulation. The characteristics of temperature, the velocity distribution and salt concentration are analysed. The results show that the overall temperature of the solar pond increases over the running time, and the maximum temperature (314K) appears in the lower convective zone. The velocity field is mainly distributed in LCZ, and the average velocity remains at the order of 10⁻⁴m/s. The salinity at the lower interface decreases linearly, while it decreases with a trend of fluctuating downward at the upper interface.