Abstract: Causality in criminal law is a rather important and complex issue both in theory of criminal law and in practice of criminal law.The answer that causality in criminal law is tenable or does not lie in the principle of unity of opposites of internal cause and external cause,the principle of unity of opposites of inevitability and contingency and the difference between cause and condition,which is finally tested by practice of criminal law.If fortuitous causality in criminal law is not tenable,necessary causality in criminal law itself is an issue.