The utility model discloses an offshore oil platform cathode protection initial polarization data detecting instrument. The data detecting instrument comprises a box body which is provided with a control panel. The box body is internally provided with a controller which comprises a data collector which is respectively connected with a data storage module and an extension board. The controller is also connected with a battery module. The data detecting instrument can carry out real-time acquisition on output signals 24 paths single-end output potentiometric sensor and 6-path differential potentiometric sensor output signals and carry out switching and storing according to the different timing requirements, the data detecting instrument can work continuously in a working period of half a year, the data collection in a long period is completed, and a data support is provided for the analysis of a corrosion state and a protection effect of an offshore oil platform.