AI (Artificial Intelligence) technology and multimedia technology are changing with each passing day, and have gradually involved in various fields. At the same time, the use of these technologies in the field of education has also effectively promoted the assessment of English classroom teaching. Since good classroom teaching is inseparable from evaluation, then scientific and reasonable teaching assessment of English classroom teaching can be guaranteed. At present, there is a lack of English teaching index assessment system for AI and multimedia technology. Therefore, this paper conduced in-depth research on improving the assessment system of English classroom teaching, and expounded on AI and multimedia technology. This paper built an assessment system for English classroom teaching based on AI and multimedia technology, and innovated and improves the assessment system. The experiment showed that 85% of the teachers were satisfied with the assessment system of English teaching indicators based on AI and multimedia technology, and 70% of the teachers were satisfied with the assessment system of traditional English teaching indicators. The new system can help to promote a more objective and scientific assessment of English classroom teaching.