The invention discloses a device for measuring the axial flow speed imaging of a friction pair fluid film with a customized slide block, including a lighting mechanism, a friction pair, a lateral optical observation mechanism and an axial optical observation mechanism. The lighting mechanism provides a light source for a fluid marker, the friction pair comprises a customized slide block, and the fluid marker is reflected by the customized slide block to form a marked virtual image. The lateral optical observation mechanism measures and records an optical image perpendicular to the thickness direction of the fluid marker, and the axial optical observation mechanism measures and records an optical image of the virtual image formed by the fluid marker. By comparing the image difference of the friction pair relative to the fluid marker at the time of static and moving, the three-dimensional flow speed measurement and analysis of the fluid in the confined gap is achieved. The device is simple and easy to operate.