  Dynamical jets are generally found on Light bridges (LBs), which are key to
studying sunspots decays. So far, their formation mechanism is not fully
understood. In this paper, we used state-of-the-art observations from the Goode
Solar Telescope, the Interface Region Imaging Spectrograph, the
Spectro-Polarimeter on board Hinode and the Atmospheric Imaging Assembly (AIA)
on board the Solar Dynamics Observatory to analyze the fan shape jets on LBs in
detail. Continuous upward motion of the jets in ascending phase is found from
the H$\alpha$ velocity, which lasts for 12 minutes and is associated with the
H$\alpha$ line wing enhancements. Two mini jets appear upon the bright fronts
of the fan shape jets visible in the AIA 171 {\AA} and 193 {\AA} channels, with
a time interval as short as 1 minute. Two kinds of small scale convective
motions are identified in the photospheric images, along with the H$\alpha$
line wing enhancements. One seems to be associated with the formation of a new
convection cell and the other manifests as the motion of a dark lane passing
through the convection cell. The finding of three lobes Stokes V profiles and
their inversion with NICOLE code indicates that there is magnetic field lines
with opposite polarities in LBs. From the H$\alpha$ -0.8 {\AA} images, we found
ribbon like brightenings propagating along the LBs, possibly indicating
slipping reconnection. Our observation supports that the fan shape jets under
study are caused by the magnetic reconnection and photospheric convective
motions play an important role in triggering the magnetic reconnection.
