A method for determining 3D primitive reciprocal basis of an unknown crystal based on a single EBSD pattern includes steps of geometrically correcting all visible Kikuchi bands with the pattern center and the detector distance used for obtaining corresponding reciprocal vectors, and determining components of the corresponding reciprocal vectors in a 3D reciprocal Cartesian coordinate system, so as to obtain a 3D primitive reciprocal basis. The method given in the present invention is able to effectively exclude fake primitive cells; correctly identify the volume of a primitive cell even though the presence of obvious errors in the width of the Kikuchi bands; and successfully determine a 3D primitive reciprocal basis of unknown crystals based on a single EBSD pattern.