The invention discloses a phase position diaphragm for a 4f phase-coherent imaging system. A diaphragm body is composed of an annular phase position object and light-pervious straps on the inner side and the outer side of the annular phase position object, the annular phase position object is formed by splicing two semi-annular phase position objects, the phase difference of one semi-annular phase position object and the light-pervious straps on the two sides is 2mphi+phi/2, the phase difference of the other semi-annular phase position object and the light-pervious straps on the two sides is 2nphi+3phi/2, and m and n are integrals. The structure of the phase position diaphragm is improved, the detection sensitivity of a 4f phase-coherent imaging method is effectively improved, and meanwhile the difficulty for processing the phase position objects is lowered.