High-fidelity photon number resolution (PNR) single-photon detectors are a key technology, but remain challenging in numerous quantum information and quantum metrology applications. Superconducting transition edge sensor has good PNR performance, but it has some problems such as slow detection speed, timing jitter, cooling and complicated readout. Here, we report an important step forward in the research of a high-fidelity PNR single-photon detector that combines near-limit efficiency detection and large-scale spatial reuse techniques using segmented double-layer superconducting nanowires. Thanks to the synergistic effect of the double-layer nanowires, the unique double-layer structure at the top of the dielectric mirror ensures near-limit detection efficiency and high signal-to-noise ratio readout. The segmented structure of each segment is shunt by the resistor to form a spatial multiplexing scheme, which constructs the mapping relationship between the pulse amplitude and the incident photon. We have prepared 8-pixel devices with 98% system detection efficiency (SDE). Further detector tomography revealed that the 2-photon and 3-photon fidelity of the 8-pixel device was 75% and 52%. In addition, our 8-pixel series nanowire detector prepared based on the 2-SNAP structure maintained a high count rate of 100 MHz at -3dB-SDE. Due to its near-limit efficiency, high photon number resolution, fast detection speed and high temporal resolution, we believe that the detector will attra