The embodiment of the invention discloses a semi-submersible type harvesting device for breeding mytilus edulis in a hanging mode. When the mytilus edulis is harvested, a submersible vehicle body is in a semi-submersible state, a floating rope is located on the top of the submersible vehicle body, in the forward moving process of the submersible vehicle body, a seedling rope to which the mytilus edulis is adhered is located in a Y-shaped fork port of the submersible vehicle body, the adhesion force of mature mytilus edulis is poor, by means of relative movement between the structure of the Y-shaped fork port and the seedling rope, the mytilus edulis gets away from the seedling rope through scraping, and the mytilus edulis sinks into a net bag due to the fact the specific gravity of the mytilus edulis is larger than that of water; the water volume of a water inflowing and draining container in the submersible vehicle body is adjusted according to the quantity of the mytilus edulis, the submersible vehicle body maintains the semi-submersible state all the time when the mytilus edulis is harvested, the water volume is adjusted after harvesting is completed, the submersible vehicle body emerges from the water, and harvesting is completed; the mytilus edulis sinks into the net bag in the harvesting process, loss of the yield of the mytilus edulis is not caused, no person is needed in the harvesting process, and the labor intensity is greatly reduced.