Abstract: A scale of language proficiency is a measurement tool used to assess and describe the candidate's language performance.Validity is the core and crucial attribution of its quality.Great efforts should therefore be made to ensure it.In the whole process of creating a scale, validity and the mechanism of its validation should be given full consideration.This paper analyzes the major aspects of the validity of a scale under development, including the construct validity, content validity, criterion-related validity and use validity.Furthermore, approaches to validation in different perspectives are proposed, emphasizing that the process of scale development and validation itself should be validated as well.