High content of chloride ions inindustrial water will accelerate the corrosion of metal equipment， A Scattering light measuring instrument which based on silver nitrate turbidimetry is used for Chloride ion detection quickly and accurately. The hardware part of the system—including the light source driving circuit，the structure beam collimation and optical current signal detection module which used Atmega128 as processor, with the use of an PIN photodetector to realize photoelectric conversion and use of a lownoise amplifier AD795 to realize currenttovoltage conversion. By measuring the standard solution, We can conclusion that it has a good stability in short time and the relative error less than 4.08%. It is proved that this scheme has good application value.