A 3-D coronal magnetic fleld is reconstructed in NOAA 11158 on 2011 February 14 by a GPU-accelerated direct boundary integral equation method (GPU-DBIE), which is about 1000 times faster than the original DBIE for solar nonlinear force-free fleld modelling, with the SDO/HMI vector magnetogram as the bottom boundary condition. The reconstructed magnetic fleld lines are compared with the projected EUV loop structures as observed by SDO/AIA at line-of-sight and the STEREO A/B spacecraft at side views. They show very good agreement three-dimensionally so that the topology congurations of the magnetic fleld can be analyzed, and the role in the flare/CME process of the active region can be better understood. It is found that the observed coronal loop structures can be grouped into a number closed and open fleld structures with some central bright loop features across the polarity inversion line which may have played a key role. A group of electric current lines co-aligned with the central bright loops along the polarity inversion line has been obtained, which conrms its important role in the flare/CME process.