This standard specifies terms, definitions, evaluation methods, detection methods and data processing methods for straightness error detection, which are applicable to straightness error detection of part elements in mechanical products. The standard describes in detail how straightness errors can be measured and evaluated in practical applications, including the concept of defining ideal and actual straight lines, and provides specific methods for measurement and data processing. As a supplement to straightness error detection in GB/T 1958, this standard ensures accuracy and conformity during the detection process. Relevant specifications and technical requirements have been cited to support the implementation of the standard.