Algebra is a fundamental topic in junior mathematic course. In computer aided education on mathematics, it is helpful for a teacher to training student‘s thinking. However, most of the mathematic application programs are very expansive and with incomplete functions. In this paper, a supporting system for algebra is proposed and implemented in Java language. In accordance with syllabus from the Department of Education, R.O.C., topics including unbounded integers, rational numbers, radical numbers, polynomials and matrices are implemented. The package TwFC is introduced to the I/O interface of our system. This paper emphasizes the arithmetic ability of radical numbers, especially focusing on the operation of denominator rationalization while inverting a radical number. The proposed algorithm can successfully execute the inverting operation with simplification of radical numbers. According to the result of our experiments, the ability of our system is more efficient than Maple and other well-known applications.