By measuring the buoyant force of common water hyacinths for common water hyacinth cultivation facilities, the mean buoyant force per common water hyacinths weight was calculated to be 11.67N/㎏ in the measurement performed based on manpower and 18.28N/㎏ in the measurement performed based on a motor. An experiment on dragging force per dragging speed according to the dragging weight was also conducted, and the experimental result verified that the dragging force increased as the dragging weight and speed increased. Moreover, the dragging force per the dragging weight according to the dragging speed was measured. Through an experiment on dragging common water hyacinths in a reservoir, it was confirmed that common water hyacinths cannot be dragged at a dragging speed of 0.036㎧ or higher owing to increased water resistance. Under the condition of the dragging weight set as 50㎏, a dragging force per unit weight of the common water hyacinth was calculated to be 2.62N/㎏ when the dragging bar was 3m in length and 2.94N/㎏ when the dragging bar was 6m in length. Under the condition when the dragging weight was set as 100㎏, the dragging force per unit weight of the common water hyacinth was calculated to be 1.50N/㎏ when the dragging bar was 3m in length and 2.13N/㎏ when the dragging bar was 6m in length. Under the condition when the dragging weight was set as 400㎏, the dragging force per unit weight of the common water hyacinth was calculated to be 0.8N/㎏ when the dragging bar was 3m in length and 5.43N/㎏ when the dragging bar was 6m in length. It was evaluated that the dragging force per unit weight of the common water hyacinth calculated in this study can be effectively applied as data for designing dragging equipment used to drag common water hyacinths in a reservoir.