Classroom-based language assessments mainly include formative assessment and summative assessment, which are the most commonly used evaluation methods. The present study adopts a contrastive method to analyze the two types of assessments. Results of the study show that: 1) the characteristics of formative assessment contain teachers' adaptation to classes and immediate feedback provided for teachers, while summative assessment, as a high-risk one, needs a high standard control and safety for dependability and effectiveness; 2) formative assessment is suitable for any places with multiple standards for the judgement of learners' achievements while summative assessment evaluates the educational effect or the whole process of special education at a certain time point, and both assessments can always be conducted on network platforms nowadays; 3) evidence and interpretation are taken into consideration in formative assessment and summative assessment respectively while the two types of assessment complement each other for the related teaching goals; 4) more attention may be paid to both assessment for learning (AfL) and assessment as learning (AaL) in the future development of assessment. The contrastive study is expected to provide a reference for classroom-based language teaching and learning.