  We have investigated the background properties of EPIC-pn onboard XMM-Newton
to establish the background subtraction method. Count rates of the background
vary violently by two orders of magnitude at the maximum, while during the most
quiet period, these are stable within 8 % at a 1 $\sigma$ level. The overall
spectrum is dominated by particle events above 5 keV, and its spatial variation
is also found. The long-term variation of the background is also investigated
with CAL CLOSED data, where the filter wheel was in closed position with the
internal calibration source illuminating the sensitive area. The average
background count rate decreased by 20 % from March 2000 to January 2001, but it
regained in February 2001. For the modeling of the background spectrum, we
investigate relations between the 2.0--7.0 keV count rate and some
characteristic parameters. The 2.0--7.0 keV background count rate shows a good
correlation with the count rate of events outside the field of view. This
correlation is usable for the modeling of the background.
