The invention discloses a valve with a valve clack convenient to replace and a replacing method. The valve comprises a lower valve body, wherein a valve seat is fixedly connected to the center of an inner cavity of the lower valve body, a sealing ring is fixedly connected to the inner wall of the valve seat, an upper valve body is arranged at the top of the lower valve body, fastening screw holesare formed in the two sides of the bottom of the upper valve body and the two sides of the top of the lower valve body correspondingly, fastening bolts are arranged in inner cavities of the fasteningscrew holes in a penetrating mode correspondingly, a valve rod is arranged at the top of the upper valve body, and the bottom of the valve rod sequentially penetrates through the upper valve body andthe lower valve body from bottom to top and extends to the top of the inner cavity of the lower valve body. Through cooperative use of the valve clack, the fastening screw holes, the fastening bolts,the valve rod, the upper valve body, a first screw, a first baffle, a sliding clamping block, a first sliding groove, a limiting clamping block, a stable sliding block, a first spring, a stable sliding groove and a limiting clamping groove which are arranged, the problem that the valve clack of an existing valve is inconvenient to replace, the replacement time is greatly increased, and the convenience of the valve is reduced is solved.