After assuming power，according to election platform，Japanese Democratic Party proposed to reform the original social security system from pension，medical，lack of children，nursing，handicapped welfare and employment，the core of which were pension system reform and countermeasures to lack of children.These reforms will face factors such as the change of population structure，the triode structure of welfare supply’s shaking and financial situation’s worsening，and these are the biggest subject that Japanese Democratic Party will face during its social security system reform.Japanese Democratic Party holding power，not only means the change of Japanese national development model from pursuit political power to livelihood priority，but also means the change of social welfare model from combination to universalism.