The invention discloses a pressing mechanism. The pressing mechanism comprises a bottom plate, a slide rail, a first slider, a second slider, a first installing plate, a pressing head assembly, a second installing plate, a push rod assembly, a driving assembly and a switching block, wherein the slide rail is fixedly connected to the bottom plate, the first slider and the second slider are slidingly arranged on the slide rail in the horizontal direction, the first installing plate is fixedly connected to the first slider, the pressing head assembly is slidingly arranged on the first installingplate in the vertical direction, the second installing plate is fixedly connected to the second slider, the push rod assembly is connected to the second installing plate, the driving assembly is usedfor driving the second slider, the push rod assembly and the first slider to move in the horizontal direction, and the switching block is connected between the push rod assembly and the first installing plate and used for converting the horizontal movement of the push rod assembly into the vertical movement of the pressing head assembly. The horizontal movement of the push rod assembly is converted into the vertical movement of the pressing head assembly through the switching block, so that a sample is extruded, a pressed object is not shielded on the upper side before and after being pressed,operations are convenient, and a wide view is given.