Physical and mathematical models for the temperature drop process of the waxy crude oil in the single-plate floating roof oil tank are established with the consideration of non-Newtonian behavior and wax precipitation, and a coupled integrative numerical procedure is developed. In this research, the non-Newtonian behavior is described by the power-law equation. The turbulent flow is calculated by Large Eddy Simulation (LES) method. Wax precipitation of the waxy crude oil in the tank is simulated by the enthalpy-porous media theory, in which the gel oil interface is tracked. The numerical program is validated by the results obtained from the literatures. Based on the verified program, temperature drop process in a single-plate floating roof oil tank is calculated, and the evolution characteristics of the waxy crude oil in the tank are studied. Furthermore, gel oil growth on the tank top and tank bottom and heat flux on tank top, tank bottom and tank wall are also investigated in this research. The research results provide guidance for the scientific designing of the single-plate floating roof oil tank and making schedule of waxy crude oil turnover reasonably.