It is one of the most important problems for engineers to know the relations between welding faults and mechanical properties of weld joints. In studing such problems, it was labourable and sometimes difficult to obtain the specimens of welds containing the weld faults with same conditions. Now in this papers, we proposed some artificial methods for each weld faults which are of same sort, same size and same distribution. By such method, we could obtain the quantitative and reproducible datas for our object. The sorts of artificial faults proposed are blow hole, slag inclusion, poor penetration, crack and undercut and as mechanical tests, static and impact tension tests, static and impact bending tests and fatigue tests were done. At last we tested the specimens containing naturally produced faults.