Constructing government ruled by law is the key to realize ruling the nation by law,and the core to build the country and society ruled by law,and it is also a systematic engineering related to a nation’s political,economic and social development.The formation of a government ruled by law follows its own rules.Government ruled by law is not a simple combination of “ruling by law” and “government”,but a constitutional integration of both in essence.Such conclusion is drawn from the correlating analysis of the general features of modern rule-of-law,the fundamental requirements of constitutional government and the key constituents of a government by law.