ABSTRACT
This study aims to aid in the development of a web-based system that can evaluate the level of words in Vietnamese sentences and will be used for teaching and learning Vietnamese. The system will show users the percentage of words containing each level of the Vietnamese vocabulary. The person who develops of teaching materials can use this system to check the level of words that are contained in a certain text and can arrange them to make the text more appropriate for the learners' proficiency. To divide the vocabulary into 3 levels is based on teaching materials that are published in Vietnam and other countries. However, the user evaluations of the system allows us to reconsider the 3-level program to make the system more useful for a wide range of learners.