  CANDLES experiment in Kamioka Underground Observatory aims to obtain the
neutrino-less double beta decay ($0\nu\beta\beta$) from $^{48}$Ca. This
measurement is a big challenge due to the extremely rare decay rate of
$^{48}$Ca. Thus, in order to obtain 0\nu\beta\beta, it is needed to reduce
background as much as possible. Series of alpha and beta decays originated from
radioactive impurities can remain as background in the energy region of
$0\nu\beta\beta$. Because they are sequential decays, we can remove them by
tagging preceding and following events. This tagging method requires minimized
dead-time of DAQ system. A new DAQ system was introduced in CANDLES with new
FADC (Flash Analog-to-Digital Converter) modules using 8 event buffers and
SpaceWire-to-GigabitEthernet network for data readout. To reduce the dead-time,
we developed our DAQ system with 4 parallel reading processes. As a result, the
read-time is reduced by 4 times: 40msec down to 10msec, which is in equivalent
to a half of previous DAQ's read-time. With reduced read-time accompanied by
multiple event buffers, the new DAQ system is realized with efficiency is very
close to 100$\%$ (no event lost at 20cps, which is CANDLES trigger rate, after
63 hours of data taking). With improved performance, it is expected to achieve
higher background suppression for CANDLES experiment.
