Abstract: There are two assessment standards——SINTAP and BS 7910 to perform a safety assessment.Both the standards have an assessment method which make use of a FAD(failure assessment diagram).The methods which measure the value of the abscissa of the FAD in the two different standards were compared and analyzed.In SINTAP and BS 7910,the abscissas of the FAD indicate the proximity to plastic collapse of the structure.That is to say,the basis of assessment is the same in two standards,but as the detail methods of calculating the values of the abscissas of the FAD are different.Furthermore,in BS 7910,when the levels of the assessment are different,the method of calculating the values of the abscissas of the FAD are different.An example was offered to give a further interpretation.When a same fracture was assessed in a same structure by using the two standard,different results were obtained because the factors which were taken account in the two standards are different.Moreover,the values of the abscissa in different levels of the assessment are different.All these interpret that the conservative degrees of the assessment are different.