This article takes a perspective from historical materialism to analyze the Marxist theory of the transformation of social forms. It makes a scientific judgment on the era we are living in and our historical orientation，and addresses scientifically some strategic issues in our development：we are living in the historical era when capitalism is heading for its doom and is going to be replaced by socialism；and in the era，the working class is in the historical orientation of engaging themselves with socialist revolution and building. This article is the first part of studies in Marxism and the historical destiny of socialism.