In order to enhance the performance of the processor for elliptic curve cryptography,an improved alogorithm of Montgomery modular multiplication is proposed,and a pipelined hardware structure for the algorithm is constructed.Then,the computation of point addition and point double of elliptic curve are optimized to fully take the advantages of modular multiplication.Thus,the point multiplication with 256b length parameters costs only 232704 clock cycles.The implementation on Cyclone II EP2C35 shows that the coprocessor needs 21000 slices and can fi-nish 1287 point multiplicaions per second for 256b length.