This paper presents high-performance Elliptic Curve Cryptography (ECC) architecture over binary field, based on the Montgomery scalar multiplication algorithm. The word-serial finite field arithmetic unit (AU) is proposed with the optimized operation scheduling and bit-parallel modular reduction. With a dedicated squarer, the 163-bit point scalar multiplication with coordinate conversion can be done in 20.9μs by the design of one AU, and can be further improved to 11.1μs by the one of three AUs, both using 0.13μm CMOS technology. The comparison with other ECC designs justifies the effectiveness of the proposed architecture in terms of performance and area-time efficiency.