Abstract: In the production process of precious metal nickel, the nickel material for extraction contains complex components such as nickel ions and impurity metal ions. The nickel ion concentration in the nickel extraction and purification solution is an important operating parameter in the production process, and on-line detection of nickel ion concentration is a necessary link to achieve optimized operation. In view of the on-line detection range of nickel ion concentration in nickel extraction process of 0.5-100 g/L, and the quantitative control method of reagent addition, this paper studies several kinds of on-line and off-line detection methods for nickel ion concentration in nickel extraction solution at home and abroad, introduces their detection principles, application occasions and existing problems. Then it proposes an on-line detection method for nickel ion concentration in nickel extraction solution based on automatic complexation titration and color soft measurement, and develops an on-line analysis instrument for nickel ion concentration based on this method. This paper introduces the working principle, composition structure, characteristics and on-site industrial online detection application effect of the instrument. The device has significant advantages such as high measurement accuracy, high reliability and intelligent control, which can completely solve the problem of online measurement and closed-loop control of nickel ion concentration in nickel extraction process, assist the automation and optimized control of the entire nickel extraction process, and stabilize the nickel ion concentration at the required range of process requirements to improve production indicators of nickel salt plant.