The invention provides a common-path interference phase microscopy one-time imaging system and method. The common-path interference phase microscopy one-time imaging system comprises a laser, a neutral adjustable damper, a beam-expanding aligner, a half transparent and half reflecting mirror, a field diaphragm, an unpolarized beam splitter prism, a reflecting objective table, a sample, a microscope objective, a third lens, a CCD (Charge Coupled Device) and a computer. The common-path interference phase microscopy one-time imaging system is based on a differential interference light path, the unpolarized beam splitter prism is used for partitioning laser light into two beams of parallel light, namely, object light and reference light, the reflecting objective table is used for reflecting the object light and the reference light totally, the object light and the reference light are combined through the unpolarized beam splitter prism and transmitted in a common-path way, and the combined light is collected by a CCD camera and transmitted to the computer to be displayed after being amplified through the microscope objective. By adopting the common-path interference phase microscopy one-time imaging system and method, the conventional path interference imaging system can be realized by adjusting the angle of the reflecting objective table, including off-axis interference, co-axial interference and slight off-axis interference. The system has a high practical value and a wide application prospect on the aspect of phase microscopy, and can be particularly applied to the field of biological cell morphological identification.