  GRANDProto35 is the first stage of the GRAND project. It will be composed of
an array of 35 radio antennas and 24 scintillation detectors, the radio and
scintillating subarrays being triggered independently. The scintillation
detector array allow to cross check,through an offline treatment, if the
selected radio candidates are indeed air shower events and thus quantitatively
determine the detection efficiency of the radio array. The Hamamatsu R7725 is
candidate for the scintillation detector photomultiplier. The characteristics
of the PMT will directly affects the time and energy resolution, dynamic
detection range of a scintillation detector.In order to cover the large dynamic
range, voltage divider circuit featured with dual-readoutwas designed for the
PMT. In this paper,details about the system setup, measurement method and
results will be described. Some characteristics of PMT were calibrated and
researched: the absolution gain, single photoelectron (SPE) energy resolution,
transit time spread (TTS), linear dynamic range and temperature dependence of
PMT gain.
