This paper compares and analyzes ISO5817 and MT/T587 one by one,which are common domestic and foreign defect standards of hydraulic support structures,main including defect categories,corresponding detection levels and acceptance levels. Main differences between domestic and foreign standards are as follows:1. Defective acceptance is only a part of MT/T587,which scope of application is more wider than ISO 5817,but it is less systematic,concrete and comprehensive;2.MT/T587 only has specific provisions on surface defects and geometric shape defects. However,it does not explain internal defects in detail and defective acceptance is only required to comply with GB/T11345 provision;3. As for surface imperfec-tions and geometric imperfections,Ⅰclass level of MT/T587 is more critical than C class level of ISO5817. Finally,counter-measures of common imperfection are formulated:1. To reduce stress concentration, it is recommended to adopt welding toe grinding;2. Both standards allow the existence of internal poro-sity and inclusion defects,but should meet the assessment limit;3.Although defect of geometric shape reduces the bearing capacity of the joint,it can increase thickness of the welding seam to compensate.