Plagiarism is an academic misconduct commonly found in the educational institutions nowadays. This paper first defines the types of plagiarism and explains the typical reasons for university students to engage in plagiarism. Then, the factors influencing plagiarism are discussed, including the access of materials on the Internet, the social norm of students and the academic policies in universities. This paper suggests an educational approach with the emphasis on the formative assessment to alleviate the problem of plagiarism. Formative assessments are more helpful when students do not need to hide their mistakes and are open about their limitations. This can provide more support for students developing their learning skills, compared with summative assessments in which students do all to suggest competence and conceal ignorance. A survey was performed to collect data about university students' attitudes to the final year project that is a kind of formative assessments. According to the result, the formative assessment is practical for students to understand plagiarism and avoid it. In addition, the learning experience from formative assessments is perceived to be beneficial in completing summative assessments.