A novel self-stable quantitative phase imaging system, based on a white light Michelson interferometer with Kohler illumination is reported. An actively stabilized phase-lock circuit is employed in the system to reduce phase noise. A phase-shifting technique is used to obtain quantitative phase images of the sample. Mirror, standard negative test chart and polystyrene beads are used as samples in experiments. Clear quantitative phase images are obtained and real-time observation is realized. The system uses halogen lamp as the light source and the vertical resolution of 5 nm is obtained. The structure of Kohler illumination in the system ensures high spatial coherence. Experimental results show this system can get rid of the interfering signal from other optical surfaces, such as lens surfaces.