Directional solidification is the most popular technique for massive production of multicrystalline siliconin the solar industry. Conventional process aims to prevent the breakage of silicon ingots. To lowerdislocation density in ingots, a significant modification to conventional cooling processes in productionsof mc-Si ingots is proposed, and a three-dimensional numerical simulation with a simplified model ofdislocation multiplication has been carried out to analyze its effect on dislocation multiplication. Theresults show that with the modified cooling process, the final dislocation density could be reduced toabout one fifth of that formed in normal cooling process.