Abstract: To analyze immunity of Grain-128 stream cipher in aspect of power analysis attack,researches were conducted.Power analyses of stream ciphers were considered to be more difficult than block ciphers' and public ciphers' in academia.In order to improve the pertinence of attack,firstly,power characteristic of stream cipher algorithm was analyzed,and the reason for the difficulty of the attack was considered to be the correlation between the attack point power and other power components.Then a strategy for evaluating rationality of the selection of attack point and initial vectors was presented based on the judgment,and a power analysis scheme of Grain-128 was proposed based on the strategy.Finally an attack simulation platform was raised based on ASIC development environment,and the attack scheme of Grain-128 was validated using the platform.Experiment results show that the attack scheme can be successfully attacked 46-bit key,confirming the effectiveness of the proposed strategy for evaluating rationality of the selection of attack point and initial vectors,at the same time the Grain-128 is unable to resist the power attack.