Online collaborative learning allows discussion to occur at greater depth where knowledge can be constructed remotely. However students were found to construct knowledge at low-level where they discussed by sharing and comparing opinions; those are inadequate for new knowledge creation. As such, this research attempted to investigate the students' behaviour and their strategies to construct knowledge during online collaborative discussions. Using the combination of content analysis and sequential analysis technique, this research found that groups those being able to construct high-level knowledge tend to negotiate on shared information. Argumentation is also found to contribute for successful knowledge construction at higher-level. This study suggests triggering argumentation and emphasizing on problem-solving tasks for better knowledge construction sustainability.