Aiming at the demands for welding heat input monitoring in the welding construction of nuclear power plant,a full digital IGBT inverter TIG welding machine with the welding heat input monitoring is designed and developed. This welding machine adopts DSP +ARM dual processor with TMS320F28335 digital signal processor and LPC2388FBD144 microcomputer,which realizes the digitalization of the main circuit control,human-computer interaction and external interface. By automatically recording the arc voltage,welding current and welding time during the welding process and manually inputting the length of the weld,the data of welding heat input is automatically calculated and displayed on the welding machine. The data of welding heat input can be saved in the local welding machine or USB flash disk through the USB interface,or can be uploaded to the host computer centralized control system for data transmission and monitoring through digital communication interface. The research shows that the welding machine can accurately record and monitor the welding heat input data during welding process,and meet the welding quality control requirements of nuclear power plant construction,which has broad application prospects.