In this thesis, we study scalar multiplication algorithms which play an important role in the field of ECC(Elliptic Curve Cryptosystem). They mainly consist in Binary method, Binary NAF method, and Sliding Window method. We compare them in terms of the computing time and analyze their computational efficiency based on the utilization of memory usage. As a result, we notice that Binary NAF method is the most efficient in the computing time among them, and the efficiency of the other methods are not bad to apply in ECC.