The central task of this study is to make sure that if we must defend socialism from a moral perspective.Cohenargued that traditional Marxists have not justified their political ideal from a moral perspective due to their's neglecting normative principles.As a result，Cohen turned to political philosophy after finished his defence to Marx's materialism theory of history.He tried to develop a philosophy of equality for Marxist political ideal.I found that the differences between Cohen and Marx is whether “justice” can be transcended，so this study focus this problem with the above title.

Firstly，this research reviewed Marx's attitude to just and right.It was for Marx believe that the most severe complaint to capitalism is not to point out that this society is unjust，but to show that it is based on the defects of production.Although we can introduced his criticism to capitalism from justice perspective，but in fact Marx just through predicting that the communist society will become out at any rate as his radical criticism to capitalism.Therefore，his main criticism to capitalism is to show that in the environment of justice the demand for justice will never be completely satisfied，and any efforts to pursuit justice will doom to failure.

Now that whether Marx's criticism still has significance？To answer this question，the paper then analyzed the responses of two typical representative of liberalism to make sure that Marx's criticism still has significance.As a most famous theory in contemporary western academia，Rawls's theory seriously absorbed in the critical ideas of Marx.But Rawls also refute Marx's some criticism.And Nozick as the representative of libertarianism，he defended the classical liberalism with a very powerful modern argument proposing against socialism.This indicates that the liberal wings not only return Marx's criticism，but argue for a ant-socialism passion.

To response the contemporary liberalism，Cohen turn to political philosophy.Therefore，in the Fourth part of this article，I introduced Cohen's response from moral philosophy and political philosophy perspective to these modern challenges.Cohen not only effectively rebut Nozick's Ant-Socialism Argument from a moral perspective，but also developed many normative theories to justify the badness of capitalism.As for Rawls，Cohen was at pains to show that the Difference Principle unlawful approved many unjust inequality.In the Fifth part，I introduce how Cohen to build the theory of justice on the basis of norms.He put forward two major principles of justice of socialism：the principle of equality and the principle of community.At the same time，Cohen argued that the most baffling problem to realize socialism is how to design the mechanism of socialism，but not selfishness of human nature.

Finally，I will returned to the question of justice itself.By exploring the misunderstanding of Cohen and Buchanan with Marx，I clarified the thought of Marx's about “Transcend the justice”.At the same time，I confirmed that Chinese characteristic socialism is a way which can transcend to liberalism，not to regress to liberalism.