It is an intelligent robot welding system suitable for H-shaped and S-shaped parts in sub-assembly. It realizes intelligent welding and efficient working for sub-assembly parts. By an off-line intelligent programming system, auxiliary three-dimensional mathematical model, visual imaging, and contact type induction locating technology, positioning of work pieces is not necessary. It can automatically identify the positions of work piece welds, automatically revoke the process database and conduct automatic welding. A welding informatization system is also developed for monitoring of all processes and counting of data to facilitate production management.