Abstract: The process of gold extraction from all-slime cyanide slurry is introduced, and the problems such as the lack of timely detection of cyanide ion concentration are analyzed, the detection and control of cyanide ion concentration are described.This paper introduces a detection method of cyanide ion concentration and the basic principle of cyanide ion concentration analyzer, the BOTA cyanide analyzer can detect the cyanide ion concentration in the leaching process in real-time and on-line, and automatically control the amount of sodium cyanide added according to the cyanide ion concentration, the control method of cyanide ion has been successfully applied in many mines in China, which provides a solution for the concentration control of cyanide ion in the cyanidation process.