The invention discloses a device for detecting sleeve grouting fullness in a grouting construction stage. The device comprises a perforated rubber plug, a transparent plastic tube, a movable rubber plug and a push-pull rod. The perforated rubber plug is arranged on a surface of the transparent plastic tube, one side of the transparent plastic tube, which is located at a small end of the perforated rubber plug, is set as a stretching section, and one side of the transparent plastic tube, which is located at a large end of the perforated rubber plug, is set as a developing section. The movable rubber plug is arranged in the transparent plastic tube and is connected with one end of the push-pull rod to form a push-pull plug, the other end of the push-pull rod passes through the transparent plastic tube and is extended to the outside world, and the push-pull rod is provided with a stopping portion which forms cooperation and limiting with an end portion of the developing section of the transparent plastic tube. The invention also provides a detection method. During grouting, a detecting device is directly adopted to block, then a position of the transparent plastic tube in a sleeve is adjusted, the push-pull plug is pulled out to the developing section during detection, and a result is judged through observing a slurry enrichment degree of the developing section. The structure is simple, operation is convenient, and quality control during a sleeve grouting construction process can be achieved.