The analog memristive switching of iron oxide (gamma-Fe2O3) nanoparticle assembly was investigated. The gamma-Fe2O3 nanoparticles were chemically synthesized with similar to 10 nm in diameter and assembled to be a continuous layer as a switching element in Pt/ nanoparticles/Pt structure. It exhibited the analog switching that the resistance decreased sequentially as repeating -V sweeps and pulses while increased as applying +V. The capacitance-voltage curves presenting hysteresis with flatband voltage shift and distortion of their shapes with respect to the applied voltage supported the redistribution of space charges in nanoparticle assembly that might induce resistive switching. The polarity-dependent analog resistance change proportional to pulse voltage, time, and number of pulses was analogy to potentiation and depression of adaptive synaptic motion. (C) 2013 AIP Publishing LLC.