This study was to verify the optimal effect of retrieval practice manipulating the ratio of retrieval practice vs. rereading and investigate whether the optimal ratio of retrieval practice is different according to the students’ academic achievement levels. So it was to verify the best ratio effect of retrieval practice. Participants were 515 college students from Shandong Province in China. They were divided into two groups(Group A & B). Each group consisted of 6 subgroups. Every student experienced all 6 methods using 6 different texts during consecutive 6 days. Based on the 6th day, they had another delayed test called delayed-2, in the same manner as in the immediate and delayed tests. The final test was carried out 4 weeks later from the terminated the learning. The findings of this study are as follows. First, there is a significant retrieval effect in the ratio of 70% regardless of the timing of retrieval. Second, there is a significant difference in every retention according to the students’ academic achievement levels. Students who performed high achievement got better retention than low achievement students. Regardless of students’ achievement levels, the optimal ratio of retrieval was 70%. The optimal ratio of retrieval is not 60%, but 70% in this study. These findings indicate that using optimal ratio of retrieval in learning is important to improve the education efficiency.