Based on the porous media model, a simplified model of stacked silicon was established to consider stacked porosity and melting deformation. This model was applied to numerical simulate the stacked silicon melting process of the quasi-single crystalline silicon casting system for photovoltaic solar application. Effects of the power ratios of side/top heaters, stacked porosity, and total power of heaters on the seed crystal melting process were studied. The results show that the melting time of silicon and the melting ratio of seed crystal depend on the power ratio of side/top heaters. Reducing the power ratio and the porosity is beneficial to the retention of seed crystal, nevertheless, it changes the interface shape after seed crystal melting. The impurities can gather in the concave region of the interface after seed crystal melting. Such distribution of impurities affects the quality of subsequent grown crystals. When the total power of the heater is below the critical value, the interface shape after seed crystal melting also changes near the edge of the crucible wall. This change can lead to uneven nucleation, which is not desirable for the production of quasi-single crystalline silicon. Therefore, the process parameters under the actual working conditions shall be configured according to the contour map, which is determined by the power ratio of side/top heaters, stacked porosity, the total power of heaters, the melting ratio of the seed crystal, and the melting state of the seed crystal.