Since continuance usage of e-learning can truly provide learning benefits, many studies have developed e-learning continuance models. A computer-based assessment (CBA) is often used for online formative assessment and thus is performed many times in a course (basically one formative assessment for one chapter/unit.). However, some students are unable to sustain and persist in a series of formative CBA activities. This study focused on developing a formative CBA continuance model. The study first investigated the moderating effect of “self-regulation” on continuance intention to continuance usage. Additionally, the study also considered the direct effect of “social influence” on continuance intention. The experiment lasted one semester and was performed in a college-level course taken by 152 undergraduates in Taiwan. During the experiment, five-time (formative) CBAs were conducted before the midterm and an additional set of five-time (formative) CBAs were conducted before the final term, so that actual CBA continuance usage of students could be observed. The results show that “self-regulation” significantly moderates the relationship between continuance intention and continuance usage. Additionally, “social influence” is a dominant determinant to continuance intention of using CBA. The proposed model also has high explanatory power. Finally, some implications of practical application and future research are also given.