Abstract: Iron is a key trace metal in the ocean, and directly affect marine primary productivity and global climate change. Since the 1980s, various in-situ iron analysis systems have been developed based on spectrophotometry, catalytic spectrophotometry, chemiluminescence, or electrochemistry, combined with flow analysis, osmotic pumps, or lab-on-a-chip technology for measuring iron in seawater and hydrothermal plume. With the advancement of ocean observatory technology, more requirements have been put forward for in-situ iron analyzers or sensors capable of long-term, continuous monitoring. This review outlines the principles, performance, advantages, and limitations of current systems developed globally. It further proposes future development directions, specifically targeting integration with seafloor observatory networks, aiming to provide valuable references for the development of future in-situ iron analysis system.