Abstract: In the directional solidification process of crystalline silicon,taking monocrystalline silicon bulk seeds and polycrystalline grain seeds as the research objects,the effects of seed crystal plane orientation,seed crystal size and inter-seed laying method on grain growth and dislocation distribution are studied. The results show that the dislocations always tend to assemble at the area of monocrystal seed joint and the probability of dislocation producing in the seed joint with same crystal seed planes is higher than which with different crystal seed planes. And（110）crystal plane grows laterally fast to occupy the growth space of（100）plane with only monocrystal seed competing. The growth space of monocrystal seed is occupied gradually by polycrystal seed growing with the two jointed and the ability of monocrystal（110）to resist polycrystalline encroachment and dislocation contrast with（100）is stronger. Meanwhile,the smaller size of monocrystal seed,the more uniform of ingot casting grain and the lower dislocation density in crystal silicon.