This study aims to investigate the effectiveness of cooperative learning for accounting skill certification test by using blog as a platform. The investigation applied quasi-experimental approach. The statistical sampling was from the second year students in the information operation department of a local private vocational academy. Students were S-type grouped into two groups, namely, experimental group and controlled group based on their academic performances. The former used blog as a platform of both teaching and cooperative web learning; the later only used blog as a teaching platform. The learning subject that is the accounting skill certification test related material is identical for both groups. After 18 weeks of application, the results indicated that the students in experimental group had better learning effectiveness over those in the controlled group with higher degree of satisfaction.