The invention provides a phase shift focus monitor reticle, a manufacturing method thereof, and a method of monitoring focus difference using the phase shift focus monitor reticle. The phase shift focus monitor reticle comprises a shield comprising a plurality of light-transmitting portions with a certain width; and a glass layer positioned on the shield layer comprising a plurality of openings at the light-transmitting portions; wherein the width of the openings is half of the width of the light-transmitting portions; the depth of the openings is n*λ/(N−1), wherein λ is the wavelength of the lights incident on the phase shift focus monitor reticle in air, N is the refractive index of the glass layer, n is a positive integer. The invention can be applied to thicker photoresist and different process machines.