The success of seaweed cultivation is highly reliant upon several related factors. This research aimed to study the development of seaweed Kappaphycus alvarezii cultivation using the longline method, observe the physico-chemical parameters of the waters, types of pests, growth and production of seaweed Kappaphycus alvarezii. This research was conducted in Kastela waters, Ternate Island District, Indonesia, during 45 days, from 23 July to 8 September 2019. The results of the research showed that the physico-chemical parameters of the waters are suitable to support the growth of seaweed K. alvarezii. This study also found 2 types of pests in K. alvarezii cultivation, namely seeded fish/Baronang fish (Siganus canaliculatus) and barnacles (Balanus sp.). The highest absolute weight growth obtained was 398 g, and the production of seaweed K. alvarezii cultivation reached 16.4623 g m-2 within a 45-day maintenance period.