Abstract: This paper introduces a kind of micro photometer with the advantages of light weight and small volume for the ionosphere detection. It can retrieve the total electron content (TEC) of ionosphere by measuring the atomic oxygen airglow in form of far ultraviolet radiation with a wavelength of 136.5 nm. The principle of detection and the design scheme of the photometer are presented. The integration and the miniaturization of the reflecting mirror, the industrial-grade FUV detector and the electronics are realized through a proper design of the lightweight aluminum reflector and the anti-interference preamplifier. The one-kilogram level micro sensor is developed, which is applicable to the micro-nano satellite for ionosphere detection. By taking the advantages of multi-orbit constellation, large amount of data can be obtained by the micro optical ionospheric detector including the TEC distribution in the global ionosphere with high spatial and temporal resolutions, to provides a technical basis of payload for networked satellite detecting in the future.