For conventional microscopes, the phase contrast imaging mode requires the configuration of special diaphragms, condenser or the addition of inserts to the objective lens, which increases the difficulty and cost of phase contrast microscopic imaging. Therefore, a method of virtual phase contrast imaging based on deep learning algorithm is proposed. Only an ordinary optical bright field microscope is required to acquire cellular bright field images, and then the bright field images are converted to phase contrast images on a computer using a deep learning method. We compare the virtual phase contrast images with the standard phase contrast images acquired by the microscope. The results demonstrate the effectiveness of this virtual phase contrast imaging method, which provides an example of low-cost phase contrast microscopic imaging.