Theoretical system of Marx and Engels doesn’t clearly propose the concept of “vulnerable groups”. But to understand the concept of “vulnerable groups” in the modern sense of Marx and Engels, “the proletariat” and “the social underclass”, ”the poor”, “the exploited classes” and other related groups, we can see that Marx and Engels’ definition of correlation. Marx and Engels, as thinkers, theorists of “the vast majority of people’s interests”, in essence, stand on the position of the weak, weak cry, to help vulnerable groups of society from oppression and poverty to be liberated. So the theory of Marx and Engels has a very rich “vulnerable groups” ideological content .This artide discusses the significance of the thought of vulnerable groups of Marx and Engels from such aspects as the theoretical source of the thought of vulnerable groups, the generation of vulnerable groups,and the paths to solve the problem of vulnerable groups.