The invention discloses a reinforcing device for a suction anchor, the suction anchor and an installation method for the reinforcing device. The suction anchor comprises an anchor barrel, and the reinforcing device comprises a base part, a web and a first limiting device. The base part is detachably fixed on the anchor barrel, a notch is formed in the base part, and the web is rotatably and fixedly connected with the base part; a convex stretching part is arranged on the web, the convex stretching part abuts against the base part when the web rotatably opens in the direction of far away from the base part, and the opened angle of the web is less than or equal to 90 degrees; and the first limiting device is fixed on the anchor barrel, the size of the end portion of the first limiting device is in fit with the size of the notch, and the first limiting device can be arranged in the notch in an inserted mode. According to the reinforcing device for the suction anchor, the suction anchor and the installation method for the reinforcing device, the technical problem that dropping out of the suction anchor occurs easily due to the fact that anchoring force depended by the suction anchor and provided by seawater pressure and barrel body friction is still limited in the prior art is solved.