In this paper, we designed a photon-number-resolving single-photon detector based on an avalanche photodiode, which used a short-pulse gated signal combining with a capacitive balanced noise suppression scheme to achieve a single-channel high-performance detection of 100 MHz with a detection efficiency of 40.5%, and effectively resolved the number of incident photons with spatial beam splitting. In order to more completely describe the quantum characteristics of the detector, we introduced the quantum detector tomography technology, starting from the single-channel single-photon detector to the dual-channel photon-number-resolving detector, performed quantum tomography calibration, reconstructed its positive-operator-valued measure matrix and the corresponding Wigner function, and established the corresponding theoretical model. The results show that the dual-channel 100 MHz photon-number-resolving detector can achieve quantum detection.