Rural minimum subsistence guarantee has not only made some rural poverty-stricken population out of poverty，but also reduced the poverty depth of such population. Research on the role of rural minimum subsistence guarantee in influencing income gap shows that the assistance of minimum subsistence guarantee has certain effectiveness in narrowing income gap among ethnic groups in the provinces and regions surveyed，but the effectiveness is limited，and inter-provincial and inter-ethnic group difference exists. The test based on Theil coefficient shows that，on the one hand，rural minimum subsistence guarantee plays a greater role in narrowing intra-provincial income gap and in narrowing intra-ethnic group income gap；on the other hand，the assistance of minimum subsistence guarantee is more favorable for the improvement of income distribution of poverty-stricken groups. Generally speaking，the rural minimum subsistence guarantee system targeting rural lowest-income families has basically reached the original intention in implementation.