Abstract: Objective Inaccurate dosing is an important cause of medical malpractice, how to adjust the medication dose to overcome the excessive deviation will be discussed in this paper. Methods Gold zone method was proposed on the basis of the probability theory and mathematical statistics for handling inaccurate dosing problems. Investigation and study in large sample size was carried out on adverse reactions of Cefamandole Nafate for Injection by adopting the method. Results The conclusions from the super large sample size test indicate that there is highly significant difference of total adverse reaction rates between taking values within and outside golden zone of dosage, and the adverse reaction rate of taking values within golden zone is significantly lower than that of outside golden zone. It is noteworthy that when dosage was lower than golden zone,the adverse reaction rate was significantly increased,which is more than 4 times of that within golden zone. Conclusion It is effective measures and simply and easy to apply that taking values within golden zone of dosage reduce adverse drug reactions,probability within golden zone less than 1/4 range of experience that contains the actual demand of the body up to 70%.