Current intensity is the basic parameter of the electrolytic aluminum process. The accurate measurement of electrolytic cell current is beneficial to improve the production efficiency and work stability. This article analyzes in principle about the reason why the fiber-optic current sensor has high accuracy in electrolytic aluminum current measurement compared with the traditional current measurement technology. To reduce the repeated disassembly and assembly error and high current temperature error of fiber-optic current sensor in field applications, innovatively proposed key technologies such as the sensing optical fiber plug-in scheme based on flexible packaging, two-dimensional compensation of temperature error and nonlinear error, etc. The handheld fiber-optic current sensor is designed and developed for the first time. The test results show that the error of the sensor under repeated disassembly and assembly is less than 0. 12% , the error when measuring 0. 5 ~ 30 kA current in the temperature range of -40℃ ~ 70℃ is less than 0. 2% . When measuring the column bus current in an electrolytic cell, the error with the displayed value in the control room is less than 0. 4% . Through the continuous monitoring and analysis of the distributed current of the cathode soft discharge, the early warning of the damage of the electrolytic cell is realized.