The utility model relates to a slurry supplementing structure which comprises a vertical slurry supplementing main barrel body, and a communicating pipe is arranged at the lower end of the slurry supplementing main barrel body and used for being connected with a slurry outlet of a grouting sleeve. And a liquid level sensor is arranged on the slurry supplementing main cylinder body and is used fordetecting the liquid level height of the grouting material entering the slurry supplementing main cylinder body. According to the utility model, the liquid level sensor is used for detecting the liquid level height of the grouting material in the slurry supplementing main cylinder without manual observation, so that the personnel demand is reduced; during use, the controller is additionally arranged, so that the liquid level sensor is in signal connection with the controller, the liquid level sensor sends corresponding signals to the controller according to the detected liquid level height, starting and stopping of the grouting pump are controlled through the controller, the control timeliness of the grouting pump is better, the convenience and the automation degree of the whole operationare improved, and the construction efficiency is improved.