A method for measuring a precision of a star sensor and a system using the same may be provided. The method may comprise steps of: 1) fixing the star sensor on the Earth; 2) inputting a current time (T) of a measuring start time relative to a J2000.0 time; 3) determining a directional vector of the navigation star in a J2000.0 Cartesian coordinate system at the current time (T) according to a right ascension and a declination of the navigation star in the J2000.0 Cartesian coordinate system and visual movement parameters (α′, δ′) of the navigation star in the direction of the right ascension and the declination which are stored in the star sensor; 4) converting the directional vector of the navigation star in the J2000.0 Cartesian coordinate system into a directional vector of the navigation star in an ecliptic coordinate system; 5) converting the directional vector of the navigation star in the ecliptic coordinate system into a directional vector (vCRFT) of the navigation star in a celestial coordinate system; and 6) converting the directional vector (vCRFT) of the navigation star in the celestial coordinate system into a directional vector (vTRF) of the navigation star in a terrestrial coordinate system, and obtaining the precision of the star sensor based on the directional vector (vTRF) of the navigation star in the terrestrial coordinate system.