  In this manuscript, the structure of broad emission line regions (BLRs) of
well-mapping double-peaked emitter (AGN with broad double-peaked low-ionization
emission lines) 3C390.3 is studied. Besides the best fitted results for
double-peaked broad optical balmer lines of 3C390.3 by theoretical disk model,
we try to find another way to further confirm the origination of double-peaked
line from accretion disk. Based on the long-period observed spectra in optical
band around 1995 collected from AGN WATCH project, the theoretical disk
parameters of disk-like BLRs supposed by elliptical accretion disk model
(Eracleous et al. 1995) have been well determined. Through the theoretical
disk-like BLRs, characters of observed light-curves of broad double-peaked
H$\alpha$ of 3C390.3 can be well reproduced based on the reverberation mapping
technique. Thus the accretion disk model is preferred as one better model for
BLRs of 3C390.3. Furthermore, we can find that different disk parameters should
lead to some different results about size of BLRs of 3C390.3 from the one
measured through observational data, which indicates the measured disk
parameters are significantly valid for 3C390.3. After that, the precession of
theoretical elliptical disk-like BLRs being considered, we can find that the
expected line profile in 2000 by theoretical model is consistent with the
observed line profile by HST around 2000. Based on the results, we can further
believe that the origination of broad double-peaked balmer emission lines of
3C390.3 are from accretion disk around central black hole.
