The invention provides a common-light-path and multi-view-field star sensor and a star attitude measurement method thereof. The common-light-path and multi-view-field star sensor shares one set of an optical system, an imaging unit and a data processing unit, wherein the optical system can be used for simultaneously observing three fixed stars in different sky regions; the imaging unit is used for simultaneously imaging the three fixed stars in the different sky regions and carrying out star map identification on imaged star points; the data processing unit is used for carrying out extraction of center-of-mass coordinates on the collected star points of the fixed stars, carrying out non-aligned revising on offsets of three view fields and finally finishing high-precision star attitude angle output. According to the common-light-path and multi-view-field star sensor, the problem that the measurement precision of a single-view-field star sensor along an optical axis direction is low can be effectively solved; meanwhile, the disadvantages that the weight, the power consumption and the volume are great, which are caused by the reason that a traditional multi-view-field star sensor adopts an optical system and an imaging system which are split, are overcome; three-axis high-precision measurement is realized and a light miniaturized design is also realized; the requirements on the high-precision attitude measurement by multiple satellite platforms can be met.