In order to understand the well-known surface pattern of oxide melt flow in a Czochralski crucible, a set of three-dimensional numerical simulations of LiNbO3 melt flow in a crucible (47 mm(phi) x 46 mm(h)) with a rotating disc (23.5(phi) mm, rotating at Ohm) was conducted using the finite-difference method. The crucible bottom was assumed to be adiabatic and the side wall was healed by a constant heat Bur. Several case studies with a constant temperature of the side wall were considered for comparison. The heat loss from the melt surface caused by radiation to the ambient at a constant temperature was taken into account. The disc/melt interface was assumed to be flat and at melting-point temperature. To investigate the role of surface tension in the melt flow, numerical simulations including and neglecting the Marangoni effect were conducted at each disc-rotation rate. When neglecting the Marangoni effect, the interaction between the buoyancy and the disc rotation produces a wavy ring-like pattern on the melt surface only at approximately Ohm = 40 rpm. However, if the Marangoni effect is taken into account, a spoke pattern appears on the surface over a wide range of disc-rotation rate (0 rpm less than or equal to Ohm less than or equal to 45 rpm). At higher disc-rotation rates, the spoke pattern disappears. The flow in the bulk can be classified into three different types according to the disc-rotation rate, i.e., (1) thermally driven axisymmetric flow with no reverse flow at low rotation rates (0-20 rpm), (2) thermally driven axisymmetric flow with reverse flow beneath the disc at moderate rotation rates (20-30rpm) and (3) nonaxisymmetric unsteady flow at higher rotation rates (greater than or equal to 40 rpm). The investigation of the effect of the thermal boundary condition indicated that these flow patterns are sensitive to the thermal boundary condition of the crucible side wall.