The solodification process of horizontal continuous cast gray iron barof 4.6 cm in diameter was simulated. The function for distribution of heat fluxon the internal surface of graphite sleeve, which is equal to that on the surface ofiron bar, was inversely derived by using numerical calculation from the tempera-ture distribution in the sleeve measured in real production. By using the distribu-tion of heat flux as a boundary condition on the surface of iron bar, numericalsimulation on solidification of iron bar taking longitudinal heat conduction intoaccount was made. The profile of solidification front obtained from numerical si-mulation was approximately similar to that in real production. In addition, thequantitative relationships of the thickness of solidified layer at the exit of crys-tallizer with the main technological parameters, including the temperature of liq-uid iron at entrance of crystallizer, the moving speed of the bar and the intensityof water cooling, were obtained by using numerical simulation.