The invention discloses an on-orbit fault early warning and detection device of a spacecraft. The on-orbit fault early warning and detection device comprises a detector shell, three groups of detection units, an energy analyzer, a low-energy charged particle detector and a high-energy charged particle detector. The three groups of detection units consist of temperature sensors and total dose sensors and are used for detecting radiation effects in an unshielded state, an equivalent shielding thickness state of a cabin wall of the spacecraft, and a total equivalent shielding layer thickness state inside the spacecraft respectively. The energy analyzer is used for detecting electrons lower than 100keV. The low-energy charged particle detector and the high-energy charged particle detector respectively detect low-energy electrons/protons and high-energy electrons/protons. According to the invention, graded detection of electrons and protons with different energy can be realized; and total dose data and dose rate data at different positions on the surface and in the spacecraft can be obtained at the same time. The on-orbit fault early warning and detection device has characteristics of multiple functions, accurate spacecraft on-orbit fault early warning, accurate fault discrimination and the like.