The invention discloses a mobile automatic feeding and pressing mechanism of a rodless cylinder. The mechanism comprises a frame; a mobile through groove is formed in the middle part of a top plate of the frame; a protective support cover is fixed at the left end of the top plate of the frame; a pressing oil cylinder is fixed on the top surface of the protective support cover; a push rod of the pressing oil cylinder penetrates through the top plate of the protective support cover, and is fixed with an upper pressing block; the bottom surface of the top plate of the frame is fixed with the rodless cylinder; the top surface of a slide block of the rodless cylinder is fixed with a mobile block; the mobile block is inserted in the mobile through groove; the front and back wall surfaces of the mobile block are tightly bonded on the front and back inner side walls of the mobile through groove; the upper end of the mobile block extends out of the top plate of the frame, and is fixed with a lower support block; an upper placing block is arranged above the lower support block; and multiple buffer springs are fixed on the bottom surface of the edge part of the upper placing block. A board to be machined can be put in a mounting groove; the rodless cylinder automatically moves below the upper pressing block to realize automatic pressing; and the upper placing block and the lower placing block are flexibly connected by the buffer springs.