A finite element model of fluid field of front-box and 3-spacer nozzle of aluminum roll-casting has been developed to provide a comparison of analyzing distribution of velocity and temperature of outlet of nozzle with variable velocity. The computation is performed by using coupled fluid-thermal FEM simulation of FLOTRAN module in ANSYS 6.0. The boundary conditions of the roll-casting model of fluid and thermal fields, were loaded on front-box and nozzle. Based on the postprocessing function of ANSYS, the strict result analysis was conducted by MATLAB. Results based on the allowable inhomogeneity of velocity and temperature of outlet show the most possible broken regions of outlet could be predicted in the case of speed increasing of the drawing-sheet and thickness reducing of the aluminium sheet. The profile parameters of the nozzle including distribution, shapes and sizes of the nozzle spacers, and shapes of inner nozzle must be optimized to be appropriate in high roll cast speed.