Double helical precessing vortex core (PVC) and its interaction with premixed propane flame in a swirl-stabilized burner is studied numerically. The model burner is operated under atmospheric pressure, swirl number S-n = 1.05 and equivalence ratio Phi = 0.5. Turbulence-chemistry interaction is treated using detached eddy simulation (DES) turbulence model, and finite-rate/eddy dissipation model (FR/EDM) in combination with a 3-step reduced mechanism. The flow field is well captured by DES and the premixed flame is well reproduced by FR/EDM. Dominant strong vortices are detected in the shear layer of the inner recirculation zone, and secondary outer vortices are found in the combustion chamber corners. Temperature and reaction zone maps reveal that the flame is mainly stabilized in the inner shear layer. Q-criterion is used to visualize the 3D behavior of the flow. It is found that the unsteady flow contains a large-scale coherent PVC with double structure. In addition, a co-rotating large-scale secondary outer vortex rotates around the PVC. The characteristics of the double structure PVC are studied by analyzing its slope and strength, as well as the wavelength of the vortex. The mechanisms of interaction between the double PVC and flame are clarified over slices perpendicular to the vortex axis of the PVC. The analysis shows that across the vortex, a high velocity gradient occurs and no flame is identified in the vortex core region. A bit far of the vortex core, the flame is found to be strongly affected by the PVC. The flame front is highly curved, wrinkled, and rolled up around the vortex. In general, the double PVC is found to play an essential role in the stabilization of the premixed swirled flame.