Relocation for poverty alleviation proves to be a successful strategy in the battle against poverty. People in the resettlement areas in Guizhou have achieved the goal of “two solved worries and three guarantees”, while the lack of oldage security has increasingly become prominent. Based on Amartya Sen's feasible ability theory, this paper uses the fuzzy mathematical method to measure and analyze the level of oldage security for the older adults in resettlement areas from four dimensions: economic security, health security, daily care security, and mental health security. Results show that the overall security level is relatively qualified. However, there are still problems in social integration, daily care, health expenditure, and work situation of older adults. To improve old-age security in resettlement areas, we need to help the older adults in resettlement areas achieve economic and health security, obtain access to daily care security and mental health security. We also need to clarify the principles and paths of oldage security supply in resettlement areas, and construct a framework of oldage security supply in resettlement areas for poverty alleviation.