This paper presents a security processor based on MIPS 4KE architecture which extends security functions of AES and ECC. Due to the different features of AES and ECC encryptions, two dedicated hardware units are employed. One is the AES function unit which is integrated into the pipeline of this MIPS-like processor, and the other is the ECC unit which works as a coprocessor to implement asymmetric cryptographic algorithms. Moreover, the instruction set extensions(ISE) of MIPS for these security functions are developed. Therefore, our security processor is not only able to handle high-intensity encryption tasks, but also compatible to the leading software development tools of industry. At last, its functionality and high performance are verified by our experimental chip.