Abstract: The rule of reversion of burden of proof in environmental tort action is to the benefit of the accuser’s relief.However，the presumed conclusion lacks reliability and accuracy due to the incomplete logical structure of the rule.The guiding judicial opinion issued by the Supreme People’s Court requires that the accuser provide preliminary evidence to testify the possibility of causal relationship before the defendant reversely testifies the non-existence of causal relationship.This makes a balance of burden of proof between the accuser and the defendant，providing sufficient scientific basis for the application of the rule of reversion of burden of proof.In the practice of environmental tort action，the accuser’s preliminary evidence is only required to reach low probability standard，including official document，expert conclusion，academic works，and epidemiological statistical approach.However，the judicial interpretation should give detailed explanation to the means and standard of testimony of preliminary evidence.

Key words: environmental tort, causal relationship, reversion of burden of proof, preliminary evidence, epidemiological statistical approach