The invention discloses an anti-falling mechanism for a slide block of a hydraulic machine. The anti-falling mechanism comprises a piston rod and the slide block connected with the piston rod, wherein a cavity is arranged in the slide block, the lower end of the piston rod is arranged in the cavity, and an anti-falling device used for preventing the slide block from falling during disconnection between the slide block and the piston rod is fixed at the lower end of the piston rod. The cavity is arranged in the slide block, then the anti-falling device is fixed at the lower end of the piston rod in the cavity, and the anti-falling device is capable of effectively bearing the slide block during falling of the slide block due to failure of connection between the slide block and the piston rod, thus a purpose of preventing the slide block from falling is achieved, the working safety of the hydraulic machine is greatly improved, and the occurrences of safety accidents are avoided.