Abstract: Electrically exploding wires(EEW) for nanoparticle preparation has advantages of being low cost, high efficiency, providing high purity, and allowing for controllable size distribution. However, spatial homogeneities in the EEW diffusion stage is a critical influence factor of the quality of nanoparticles. In this paper, an experimental system was designed and constructed to investigate EEW, and the ultrafast optical diagnoses, including laser imaging, multi-frame photography, and emission spectrum analysis, could be realized. Various spatial inhomogeneities, including coronal plasma, spindle structures, zipper-like structures, stratification structures, local hot spots, gaps, and residual cores, were observed. The causes of these inhomogeneities were summarized as follows: atmospheric discharge, radial inhomogeneous vaporization, thermal instability, and magnetohydrodynamic instability. A quantification method and the criteria of spatial homogeneity were established based on photographs. The effects of ambient pressure and current parameter on resistive stage and energy deposition were obtained. Moreover, the suppression methods of spatial inhomogeneities were proposed, including increasing ambient pressure and current rise rate. Ultimately, the parameter selection method for homogeneous EEW was determined.