Digital holographic microscopy apparatus with pre-magnification has been set up, which can well acquire the quantitative phase images for living biological specimens. In addition, a series of digital holograms can be automatically recorded and movies of holographic phase images of living biological specimens can be created. The accuracy of quantitative imaging is verified by a self-produced stepped transparent sample with known height and refraction. Onion epidermal cells and red blood cells are measured and quantitative high-quality phase images are obtained. The movies of phase images for paramecium are achieved. Experimental results demonstrate that the established system can achieve real-time quantitative high-resolution holographic phase image and can be effectively applied to living biological specimens phase imaging.