  The Jiangmen Underground Neutrino Observatory (JUNO) is proposed to determine
the neutrino mass hierarchy using a 20 kiloton underground liquid scintillator
detector (CD). One of the keys is the energy resolution of the CD to reach <3%
at 1 MeV, where totally 15,000 MCP-PMT will be used. The optimization of the
20-inch MCP-PMT is very important for better detection efficiency and stable
performance. In this work, we will show the study to optimize the MCP-PMT
working configuration for charge measurement. Particularly, the quality of PMT
signal is another key for high-precision neutrino experiments while most of
these experiments are affected by the overshoot of PMT signal from the positive
HV scheme. The overshoot coupled with positive HV which is troubling trigger,
dead time and precise charge measurement, we have studied to control it to less
than 1% of signal amplitude for a better physics measurement. In this article,
on the one hand, the optimized HV divider ratio will be presented here to
improve its collection efficiency; on the other hand, we will introduce the
method to reduce the ratio of overshoot from 10% to 1%.
