  A large-scale, horse-shoe-like filament was investigated and the magnetic
field around it was reconstructed. This is an intermediate filament (IF) that
appeared on the solar disk for the first time at 02:00 UT on 2015 November 7,
and took 8 days to move to the central median on the solar disk. The active
region AR 12452 around which the filament occurred was diffuse so that the
magnetic field nearby was weak, the average field strength is 106 G. Therefore,
the existing approaches to extrapolating the coronal magnetic field and to
constructing the filament configuration in the region with strong background
field do not work well here. On the basis of the regularized Biot-Savart laws
method, we successfully constructed a data-constrained, non-linear force-free
field configuration for this IF observed on 2015 November 14. The overall IF
configuration obtained in this way matches well the morphology suggested by a
304~\AA \ image taken by the Atmospheric Imaging Assembly on board Solar
Dynamics Observatory. Magnetic dips in the configuration were coincident in
space with the H$\alpha$ features of the filament, which is lower in altitude
than the features seen in 304~\AA. This suggests that the cold plasma fills the
lower part of the filament, and hot plasma is situated in the higher region. A
quasi-separatrix layer wraps the filament, and both the magnetic field and the
electric current are stronger near the inner edge of the filament.
