Kelp (Saccharina japonica) is one of the main seaweed aquaculture species in China and is crucial for environmental carbon sequestration and the development of the marine economy. However, longline aquaculture technology of kelp has been used for many years and there are many problems in the kelp aquaculture industry. Owing to the lack of mechanization modes, such as high labor costs and low profits, the mechanization of production operations is difficult. Rongcheng, in Shandong Province, is a prominent kelp aquaculture area. In the present study, longline aquaculture of kelp was the experimental object in the Sanggou Bay, Rongcheng, and a preliminary study on the mechanization of kelp aquaculture was conducted. There were two different single-rope aquaculture modes with kelp-seeding rope hanging spaces of 1 m and 2 m (A1 and A2) in the Sanggou Bay; the traditional aquaculture mode (zone B) was used as the control. By analyzing the differences in kelp growth under different aquaculture modes and the relationship between light intensity, water depth, and kelp growth in the single-rope aquaculture mode, we explored the optimal hanging space for kelp growth under this mode, which will provide important references for the mechanization and sustainability of kelp aquaculture. The results showed that the specific growth rate of kelp in the traditional aquaculture mode was higher than that in the single-rope aquaculture mode during the aquaculture period. The kelp in the upper layers of A1 and A2 grew well, with an average wet weight of 1005.35 g in the upper layer of A2, whereas the average wet weight of kelp in the traditional mode was 1254.09 g which was approximately 1.25 times of A2. The experiment lasted until the kelp was harvested. The temperature in the kelp aquaculture area was within the suitable range for the growth of kelp. Light intensity in zone A was mostly higher than that in zone B, which effected the growth of kelp to a certain extent, resulting in a lower wet weight of the kelp harvested in zone A compared to the traditional aquaculture mode. By analyzing the relationship between light intensity and water depth and the experimental results, it was found that insufficient light intensity in the lower layers of A1 and A2 led to poor growth of kelp, compared with those in the upper and middle layers. In this study, the average yield of A1 raft frame was about 690 kg whereas that of A2 raft frame was about 900 kg, which was 1.3 times that of A1; the average yield per raft under the traditional aquaculture mode was about 1420 kg, which was about 1.5 times that of A2. However, the maximum wet weight of a single kelp in the single rope aquaculture area could reach 1729.07 g, which is consistent with the maximum wet weight of a single kelp in traditional aquaculture. Although the yield of kelp in the single-rope aquaculture mode was not as high as that in the traditional aquaculture mode, the labor cost of the longline aquaculture mode was significantly reduced, which could compensate for the reduced yield. It is necessary to maintain a balance between kelp growth and improvement of comprehensive efficiency in aquaculture production. Therefore, by appropriately increasing the hanging spacing and reducing the water layer of the range, thereby allowing all kelp to receive uniform light intensity, the quality of kelp can be improved, technical support for kelp aquaculture can be provided, and the foundation for the realization of mechanized production operations for kelp aquaculture can be laid.