This study developed a mobile-memo system that supports the knowledge acquisition and posting-question to assist learners' learning in a ML (mobile learning) environment. To understand the effectiveness of our proposed system, the data were collected from the system logs, such as the elements of multimedia used in posting-question and a questionnaire regarding the students' learning attitude as well as satisfaction towards the use of the mobile-memo system. The experimental result showed that the mobile-memo was effective for learners to gather information in construction and reflection during the learning activities. In other words, the mobile-memo system can effectively support learners to acquire knowledge and post question relating to the learning course contents during learning activities. (Contains 3 tables and 3 figures.)