Abstract: This study intended to develop an online collaborative after-class tutoring platform to facilitate students in reviewing materials that have not been totally caught on in lecture This platform is problem-based, and supported by a blended scaffolding strategy that combines meta-cognitive and procedural scaffolding Students are able to employ this platform to re-construct knowledge, share knowledge, so as to approach their goal and solve problems We assumed that the blended scaffolding is able to provide such facilitations In this study, a collaborative discussion platform was created, the blended scaffolding was provided, and the effects of blended scaffolding scheme were explored in terms of learning performance and learning attitude We also examined how learner’s prior knowledge and engagement on constructive activities would affect the learning outcomes The subject-matter for instruction is Fundamental Statistics for graduate students Results indicated that providing blended scaffolding support does not elevate student’s learning achievement, neither the learning attitude However, we found that student’s prior knowledge may influence online engagement, and consequently affect learning attitude Further investigations with larger simple sizes on these two variables in relation to scaffolding supports are suggested