Earlier program plagiarism check systems are performed by using simple text, attribute or token string base on match techniques. They have difficulties in checking program styles which have nothing to do with program syntax such as indentation, spacing and comments. This paper introduces a plagiarism check model which compares syntax-trees for the given programs. By using syntax-trees, this system can overcome the weekness of filtering program styles and have advantage of comparing the structure of programs by syntax and semantic analysis. Our study introduces syntactic tree creation, unparsing and similarity check algorithms about C/C++ program plagiarism checking for internet cyber education and estimate plagiarism pattern.