The kelp, Saccharina japonica var. ochotensis, is one of the most important fisheries resources for Northern Hokkaido, Japan, and Southern Sakhalin, Russia. Recently, the resources are decreasing in two areas, it make serious issues. Based on previous studies, we guess that warmer water temperature bring poor nitrate and higher grazing pressure of sea urchin for kelp, it cause decreasing the production of the kelp. However, it has not yet confirmed in kelp ground, so oceanographic condition during winter season (February) and biomass of kelp and sea urchins during summer season (from June to August) were observed in Hokkaido (Otaru and Rishiri) and Sakhalin (Yablochnyy and Bogdanovitch). At the most warm station, Otaru, there is no kelp but many long-spine sea urchin Strongylocentrous nudus appeared, whereas the most cold station, Yablochnyy, have abundant kelp and short-spine sea urchin S. intermedius. Concentration of nitrate does not show much difference among each station. In this study examined affection of water temperature, nitrate, grazing pressure of sea urchin for kelp. It is clear that water temperature and the grazing effects for kelp, but nitrate does not show efficiency for the kelp ground.