Some BOSS welds in nuclear power plant are found to contain many defects,such as incomplete fusion,slag,porosity and so on. Causes of BOSS weld defects are investigated and analyzed to be lack of experience for welders,improper implementation and control of the welding process,etc. Based on the conditions of defects and sites,some types of potential solutions（including localized repair,replacement of new pipes or BOSS,Overlay welding,evaluation & monitoring） are put forward to deal with the BOSS weld defects in various situations. Based on the experience,the optimum suggestions of groove angle,welding process and non-destructive inspection of BOSS weld are put forward,to reduce the probability of BOSS weld defects and enhance the safety and economy of the nuclear power plants.