2010, kaspi et al. 1996, 2000, 2005, 2007, Peterson et al. 2004). The simple correlation between the BLR size and the line width for part of those objects can be found in the corresponding literatures. Here, NGC5548 is selected as our target, because there is one well sample of fine spectra with homogeneous high-quality for NGC5548 (Bentz et al. 2007, Dietrich et al. 1993, Korista et al. 1995, Peterson et al. 1991, 1992, 1994, 1999, 2002, 2004, Popovic et al. 2008, Sergeev et al. 2007, Shapovalova et al. 2004, Wanders & Peterson 1996). Some detailed information about the spectra of NGC5548 can be found in the website of the AGNWATCH project. Here, we mainly focus on the spectra studied in detail in Wanders & Peterson (1996) and collect the spectra with necessary corrections having been done by Wanders & Peterson, i.e., the collected 247 spectra have been scaled through the van Groningen-Wanders method, and have the underlying continuum subtracted, and have the narrow components removed as well, and no further corrections are necessary for the following measured line parameters. Then based on the collected 247 spectra of NGC5548 observed from Dec. 1988 to Sep. 1993., the line width and the 