Cracking in Nd: YAG laser crystals grown along <111> by Czochralski method is often observed. The growth defects in the cracked Nd:YAG crystal were investigated with optical microscopy, scanning electron microscope(SEM), X-ray diffractometry and optical absorption method. There are a lot of inclusions in cracked crystal, whose composition deviates from the normal composition of crystal. The dislocation density is so high that the phenomenon of pile-up occurs. Some micro-cracks was observed in dislocations etch pit. Cracking results from stress concentration caused by inclusions, which is caused by components overcooling, fluctuating of growth rate and asymmetry of temperature gradient in later period of crystal growth.