Abstract: After the sample tested positive,the athlete who wants to show his no fault should prove how the prohibited substance enters his body and that he has exercised the utmost caution.The mistake of fact,the mistake of the third party,the absence of conduct capacity,and the contaminated dairy food can prove the no fault.The athlete can prove his no significant fault when he reasonably trust a doctor or exercise the effort in good faith or when he is young and inexperience or honest or meet the emergence.The jurisprudence of the court of arbitration for sport about the proof of degree of fault is favorable toward heighten the effect of anti-doping combat,but it's unduly care way is easy to cause injustice and the jurisprudence is lack of guiding effort.It is suggested that the court of arbitration for sport consider the “cost and benefit” standard and the world anti-doping agency,decrease the supplements which can be chosen by the athlete and explain the anti-doping code in details by summary the valuable jurisprudence to clarify the conduct standard for the athlete.