Author gives a new analysis of K. Marx’s famous work “Forms of Pre-capitalist Production”. Author argues that the theme of this work is not specitically about the evolution of social formations as people thought before,but about the problem of the genesis of capitalism. So in this work Marx made a comparison between capitalism and all pre-capitalist modes of production,emphasizing the differences between the two,but not the differences among all pre-capitalist modes of production. In particular Marx didn’t expound on slavery and serfdom. So an inextricable historical riddle remaines. Some haven’t understand this theme and raises doubts whether slave society exited,arguing that before capitalism there existed only one social formation. This is a misunderstanding and misreading of Marx’s work. Author gives a new analysis of K. Marx’s famous work “” Forms of Pre-capitalist Production ". Author argues that the theme of this work is not specitically about the evolution of social formations as people thought before, but about the problem of the genesis of capitalism. So in this work Marx made a comparison between capitalism and all pre-capitalist modes of production, emphasizing the differences between the two, but not the differences among all pre-capitalist modes of production. In particular Marx did not expound on slavery and serfdom. So an inextricable historical riddle remaines. Some have not understand this theme and raises doubts whether slave society exited, arguing that before capitalism there exists only one social formation. This is a misunderstanding and misreading of Marx’s work.