Abstract: Abstract: From ‘buffett tax’ to ‘unequal cost’ by Joseph Stiglitz.From ‘Piketty tax’ to 2015 Nobel prize-winning economist Angus deaton,who is award by attention to the problems of the income gap. Income gap is always accompanied by human society development for a long time, which is unable to avoid and has the very strong practical research value.We begin this article with the analysis on the debate of the ‘Capital in the Twenty-First Century’,and discusses the background and feasibility of the Piketty tax. We respectively analyze the status of the income gap and the current situation and difficulties of the social security system according to European countries, America, east Asia and Latin American countries,aimed to explore the realistic origin of Piketty tax. Then we analyze the situation of the income gap and the social security system of China.we give the details supporting measures about Piketty tax: The reform of tax system and distribution system; Draw experiences and lessons from the historical experience of western developed countries;The implementation of inclusive growth of fiscal and taxation reform.Strengthen and improve the system of tax regulation of ‘walking on two legs’ and the social security at the same time.We should pay attention to the restraint of the ‘public welfare impulse’ of government and residents and build a more sustainable system of public financial revenue and expenditure.