The waters of Ternate Island, especially the waters of Kastela, have a large potential for seaweed availabilty in natural waters, but until now the development of cultivation has not been optimal due to the lack of information and technology of the right development method. Therefore, a sustainable cultivation development policy was needed.  Seedling spacing is one of the technical factors that affect seaweed growth. The purpose of this study was to determine the application of the use of the longline method cultivation in supporting the development of seaweed Turbinaria ornata cultivation through planting distance treatment and determining the best planting distance. The construction of seaweed Turbinaria ornata  cultivation is rectangular in size (25 x 10 m), made of polyethylene rope studded with concrete anchors. In the construction of the cultivation, there are five stretch ropes. Each stretch rope is installed with a distance of 25cm. The collection of seaweed seeds was carried out naturally by collecting seedlings from the research location, namely in the waters of Kastela, Ternate Island District. The collection of seaweed T.ornata seedlings was carried out at a depth of about 1 meter. The data analyzed were absolute weight growth data and relative growth rate. The results showed that planting distance had a very different effect on the growth of absolute weight and relative growth of seaweed Turbinaria ornata. The planting distance of 25cm gives the best results on the growth of absolute weight and relative growth of seaweed Turbinaria ornata.