A processor with an elliptic curve cryptographic algorithm and a data processing method thereof are shown. The processor has a first register storing a Hash value pointer, a second register storing a public key pointer, a third register storing a signature pointer, and a fourth register for storage of a verified result. In response to a first elliptic curve cryptographic instruction of an instruction set architecture, the processor reads the Hash value of the data by referring to the first register, obtains the public key by referring to the second register, obtains the digital signature to be verified by referring to the third register, performs a signature verification procedure using the elliptic curve cryptographic algorithm on the Hash value based on the public key and the digital signature to be verified to generate the verified result, and programs the verified result into the fourth register.