Abstract: The existing straightness evaluation methods for fully mechanized mining faces adopt planar straightness, describing straightness through information from a single piece of equipment such as a hydraulic support or a scraper conveyor, without considering external factors or the relative relationships among equipment. As a result, they cannot accurately and comprehensively reflect the actual straightness of a fully mechanized mining face under real working conditions. To address these issues, an overall three-dimensional spatial straightness evaluation method for fully mechanized mining faces was proposed. In three-dimensional space, based on a three-level coordinate system, the straightness of a single piece of fully mechanized equipment was evaluated using the degree of deviation between the trajectory of both the scraper conveyor and hydraulic support group and their own straightness baseline. On this basis, the evaluation of overall three-dimensional spatial straightness of the fully mechanized mining face was conducted by integrating the curved coal seam surface, equipment deviation, and advancement errors of the floating connection mechanism. Compared with two-dimensional planar straightness, the proposed method based on three-dimensional spatial straightness reduced errors and effectively eliminated the distortion effect caused by planar projection. The use of overall equipment straightness effectively solved the problem that the straightness of a single piece of equipment could not represent the overall straightness of the fully mechanized mining face. By considering the coupling relationship between the coal seam and the equipment and the lateral movement of the scraper conveyor, the straightness calculation and evaluation became closer to the actual working conditions, significantly improving the accuracy of straightness evaluation. The experimental results showed that the straightness evaluation results obtained by the proposed method were close to those obtained using the standard deviation method, verifying its accuracy. In addition, through multi-aspect deviation evaluation, the factors that may affect straightness at a specific moment could be dynamically analyzed and adjusted in real time.