  In this work, we revisit the size-luminosity relation of the extended narrow
line regions (ENLRs) using a large sample of nearby active galactic nuclei
(AGN) from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA)
survey. The ENLRs ionized by the AGN are identified through the spatially
resolved BPT diagram, which results in a sample of 152 AGN. By combining our
AGN with the literature high-luminosity quasars, we found a tight log-linear
relation between the size of the ENLR and the AGN [O III]{\lambda}5007{\AA}
luminosity over four orders of magnitude of the [O III] luminosity. The slope
of this relation is 0.42 $\pm$ 0.02 which can be explained in terms of a
distribution of clouds photoionized by the AGN. This relation also indicates
the AGN have the potential to ionize and heat the gas clouds at a large
distance from the nuclei without the aids of outflows and jets for the
low-luminosity Seyferts.
