The present paper proposes a validation framework to assess the quality of formative assessment ( FA) on the basis of studies of FA validity and reliability． Following Messick's ( 1989) “unified view of validity”，the framework argues for the key role of social-cultural context and the specific classroom context in which the teaching and assessing stages of assessment system works． Validity of FA indicates whether and to what extent the interpretation and use of FA results facilitate students’ learning． Evidence to verify FA is supposed to cover construct，task，process，interpretation as well as use of assessment results， consequence and classroom context． Based on AUA framework of Bachman and Palmer( 2010) ，the main questions needed to answer and the ways to collect evidence in validating FA are discussed in detail．