The etch pits of dislocations in Bi12GeO20 crystal at (100), (110) and (111) planes have been studied by means of chemical etching. The pattern of etch pits are very special compared with the common cubic system crystal, and we have analyzed it with theory of symmetry group. The patterns of etch pits by theoretical analysis are in conformity with the experiment. It shows that the pettern of etch pits of dislocations consists of 112 planes. It is clear that the habitual plane of crystal of Bi12GeO20 crystal is 112 plane.