Borehole strain observation is an important mean in the study on the crustal movement，and plays an important role in earthquake precursor observation. This paper introduces characteristic of borehole strain observations, the latest research progress in borehole strain observation in developed countries such as Japan, the United states etc., provides nowadays the borehole strain observation equipments and their performances, and finally discusses China's supervision network of borehole deformation and experiment of deep borehole comprehensive observation system.