Abstract: In this paper, technical analysis is performed in detail on the weld cracking of buffer tank nozzles of reciprocating compressors which happened in the West-to-East Gas Pipeline. Apart from macroscopic analysis, chemical composition analysis and metallographic analysis, visual inspection and magnifying inspection are carried out on the fractures of the weld cracking. Through these activities, the cause of the weld cracking is diagnosed as mechanical fatigue which is generated by stress and periodic cyclic loading at the welding points of buffer tank nozzles. Based on the analysis, multiple effective improvement measures are proposed for buffer tank nozzles, including installation of reinforcing pads for rigid reinforcement, baffle installation, welding detection and heat treatment.