Abstract: Power analysis attack has become one of the most serious threats to break embedded security chips. It can crack security chips much faster than exhaustive search methods. It is a new attack method of secret key. Power analysis attack and its defense have attracted much attention in recent years. First studied in this paper are the power models that can be used for power analysis attacks and defense. It is pointed out that the high-performance and general-purpose model of power analysis attacks remains a very important research in the current. Then the authors discuss various types of power analysis attack and defense techniques, beginning from simple power analysis attack, differential power analysis attack to high-order power analysis attack. The success rate of a high-order power analysis attack is higher than that of the others, but its time and complexity of calculating are higher. Defense techniques on the algorithm level and circuit-level are also presented. Algorithm level is flexible to achieve, easy to transplant, and the realization of circuit-level is difficult, but it can gain better defense. Through the discussion and comparison, this paper can help researchers design a proper solution to defend against various power analysis attacks for their particular embedded security chips, and they can also gain useful information about power analysis attacks. Finally, the future research direction on power analysis attack and defense is presented.