Abstract: In this paper the growth technique of Pb²MoO⁵, single crystal is described.It is suggested that the chief reasons for the frequent occurrence of cracks during the crystal growth be forming twins and subgrains, and the other reasons be thermal stress and inclusions. The process of forming slips caused by dislocation increase, stacking faults and twins are analysed, as well as the inclusions in the crystal are analysed. A method of preventing cracks is porposed.