In this paper, we studied the birefringence topography of bismuth germaniun oxide which hare a strong natural optical activity. It is discovered that the natural optical activity of the crystal may be compensated completely with a reflection polarised light microscopy so that the birefringence images of dislocations and subboundries were observed. The Burgers vectors of dislocations were found to be of the type of 1/2 ( 111), (100) and (110).