The invention discloses a method for improving precision of a spaceborne linear array static infrared horizon sensor. The method comprises the following steps of initial judgment of an earth-space boundary position, selection of a reference signal, normalization of a detector signal, selection of a boundary judgment element, high-precision detection of the earth-space boundary position, and high-precision altitude calculation. Combined with the characteristics of the horizon sensor and based on the characteristic that a detection element signal corresponding to a transition zone changes regularly with the movement of the earth-space boundary in a field of view of the detector, the invention creatively provides a method for locating the earth-space boundary position highly precisely by theboundary judgment element to improve the measurement precision of the horizon sensor. By the invention, the problem that an instantaneous field of view angle of a detection element, the measurement precision and the altitude measurement range are restricted mutually in the design of the conventional horizon sensor is solved. The method has the characteristics of small calculation quantity and high generality, and is easy to implement, so the method can be applied to spaceborne linear array static infrared horizon sensors with different orbit heights.