Laser + GMAW–P (pulsed gas metal arc welding) hybrid welding is a combination of laser welding with GMAW–P which can not only bring the advantages of heatsources used in these two welding processes into full play, but also compensate for each other’s drawback. Therefore, laser + GMAW–P hybrid welding is a promising joining technology for industrial applications. With its applications becoming more widespread, there is a growing need to understand more deeply of this new welding process, such as the relationship between process parameters and weld quality. As the key factors determining weld quality, the thermal field characteristics of HAZ (heat affected zone) in welding, such as HAZ width and thermal cycle parameters, have significant effects on the microstructure and properties of welded joint. In this paper, an adaptive combined heat source model developed for laser + GMAW–P hybrid welding was employed to conduct the numerical analysis of thermal field in hybrid welding. The influence of different arc power levels on the HAZ width and thermal cycle parameters in hybrid welding is quantitatively analyzed, and the relevant data obtained respectively during single laser welding, single GMAW–P and laser + GMAW–P hybrid welding are compared to each othe. It has bn found that the HAZ width is less in hybrid welding than in GMAW–P even if the poweinput of lasr + GMAW–P hybrid welding is 2 kW largr than that of GMAW–P. When the arc power is lower, there is a small difference of HAZ width between GMAW–P and laser + GMAW– P, while the difference is narrowed down when the arc power becomes higher. Laser + GMAW–P hybrid welding causes a larger cooling time and lower peak temperature which are benificial to the improvement of microstruture and properties of HAZ. The results are very useful for demonstrating the process features and understanding more deeply the advantages of hybrid welding.