  We aim to clarify the link between mass accretion and ejection by analyzing
DG Tau's jet observations from optical and near-infrared data spanning 1984 to
2019, alongside photometric variations between 1983 and 2015. We classified 12
moving knot groups among 17 total knot groups based on their constant proper
motions and comparable radial velocities. A strong correlation emerges between
deprojected flow velocities of the knots and the photometric magnitudes of DG
Tau. From 1983 to 1995, as the deprojected ejection velocities surged from
$\sim$ 273 $\pm$ 15 km s$^{-1}$ to $\sim$ 427 $\pm$ 16 km s$^{-1}$, the
photometric magnitudes ($V$) concurrently brightened from 12.3 to 11.4.
Notably, when DG Tau became brighter than 12.2 in the $V$ band, its ($B-V$)
color shifted bluer than its intrinsic color range of K5 to M0. During this
period, the launching point of the jet in the protoplanetary disk moved closer
to 0.06 AU from the star in 1995. Following a $V$ magnitude drop from 11.7 to
13.4 in 1998, the star may have experienced significant extinction due to a
dust wall created by the disk wind during the ejection of the high-velocity
knot in 1999. Since then, the magnitude became fainter than 12.2, the ($B-V$)
and ($V-R$) colors became redder, and the deprojected velocities consistently
remained below 200 km s$^{-1}$. The launching point of the jet then moved away
to $\sim$ 0.45 AU by 2008. The prevailing factor influencing photometric
magnitude appears to be the active mass accretion causing the variable mass
ejection velocities.
