Beneficiaries’ subjective evaluation is an important perspective of social policy evaluation. Based on questionnaire data analysis，this paper found that respondents from western ethnic areas gave a high rating to anti-poverty effect of social security system. The evaluation showed three characteristics：First，respondents’ satisfaction of coverage，treatment and management was in descending order. Second，northwest ethnic areas respondents’ satisfaction to anti-poverty effect was higher than southwest ethnic areas respondents. Third，respondents gave a higher satisfaction rating to Minimum living security system，while the pension system got the lowest satisfaction rating in anti-poverty effect evaluation. The study found that the causes of insufficient anti-poverty effects of social security system in western ethnic areas included：weak local fiscal capacity，weak project management，lack of medical resources，labor mobility，treatment level gap and weak sense of insurance.