In this study, the melt-thermal effect on the silicon crystal was investigated in a cusp magnetic Czochralski process. The silicon melt motion and thermal field were numerically obtained for various system variables. The crucible rotational rate from 6 to 14 rpm, the silicon single-crystal rotational rates from - 10 to - 20 rpm: the cusp magnetic field strength with the range of 0.15-0.3 T and the radii and vertical distance from the melt-solid interface of the countercurrent loops were adopted as system variables. The melt-thermal effect on the solid was represented by total heal flow to the crystal at the melt-solid interface. It was found that the crucible rotational rate, the magnetic field strength and the radii of the loops had significant effects in the melt-thermal effect on the solid and the melt-thermal effect showed nonlinear behavior due to the nonlinearity of the melt motion for the magnetic field strength and the radii of the loops. (C) 2000 Elsevier Science B.V. All rights reserved.