The teaching system in Taiwan is currently based on large classes where teachers cannot control student situations totally. In E-Learning System, a teacher who reviews a student's learning situation must examine the students' learning records according to different items, and further organize and define the students' current learning situations, which is inconvenient for the teacher. This study proposes two stages cooperative learning strategy for diagnosing and improving learning effect of students. At the self-learning stage, students are learning individually. The proposed system diagnoses students' learning situation with ability indicator. Teachers and students can obtain the last learning situation by using OLADS at any moment. At the mutual learning stage, this study conducts the experiment by grouping and according to the figures, and complementary ability grouping is more effective than random grouping. In the learning evaluation, the learning effectiveness of the experimental group is significantly higher than the control group of students. The experiment shows that students at the mutual learning stage can enhance learning effectiveness by group discussion and complementary abilities.