ABSTRAKSI: Plagiarisme atau lebih dikenal sebagai plagiat sudah tidak asing lagi di telinga kita. Apalagi di kalangan para mahasiswa dengan tugas yang begitu banyak, tidak terelakkan lagi tindakan plagiat pasti akan mewarnai dunia pendidikan. Sebenarnya plagiat dapat diatasi dengan membangun sebuah sistem yang mampu mendeteksi kemiripan antar dokumen. Banyak algoritma yang dapat dipakai dalam membangun sistem ini, seperti Rabin Karp, Smith Waterman, Edit Distance, dan lain-lain. Semua algoritma tersebut mempnyai kelebihan masing-masing. Namun algortima Edit Distance menawarkan proses perbandingan yang lebih cepat dan akurat. Untuk menambah keakuratan sistem diperlukan proses preprocessing. Proses preprocessing berisi case folding, tokenizing, filtering, dan stemming.Kata Kunci : Kata Kunci : Plagiarisme, Edit Distance, Preprocessing, String MatchingABSTRACT: Plagiarism, or better known as plagiarism is not foreign to our ears. Moreover, among the students with so many tasks, it was inevitable plagiarism will surely coloring educational word. Actually, plagiarism can be solved by building a system that capable to detecting the similarity among documents. Many algorithms that can be used to building these systems, such as Rabin Karp, Smith Waterman, Edit Distance, etc.. All these algorithms have advantages each other. But Edit Distance algorithm offers the comparison process more quickly and accurately. To increase the accuracy of the system required preprocessing process. Preprocessing process contains case folding, tokenizing, filtering, and stemming.Keyword: Keywords : Plagiarism, Edit Distance, Preprocessing, String Matching