The embodiment of the invention provides a pixel demarcation layer and an OLED (organic light emitting diode) device, and relates to the technical field of display. The attenuation state of luminous materials of each pixel unit can be identical, and in addition, the color staining caused by solution overflow can be avoided. The pixel demarcation layer comprises a plurality of openings, wherein each opening comprises a bottom surface opening, a top surface opening and a side wall, the openings at least comprise a first opening for limiting a first pixel unit and a second opening for limiting a second pixel unit, the first opening is filled with first pixel luminous materials, the second opening is filled with second pixel luminous materials, the attenuation speed of the first pixel luminous materials is lower than the attenuation speed of the second pixel luminous materials, the bottom surface opening area of the first opening is smaller than the bottom surface opening area of the second opening, the side wall of each opening is provided with a preset reference surface, the space limited by each opening comprises a main body space in the reference surface and an expansion space outside the reference surface; the expansion space size of the first opening is greater than the expansion space size of the second opening. The pixel demarcation layer is used for preparing the OLED device.