Self-assembly in near-field electrospinning is reported for the first time in this paper, which realized the conversion from two-dimensional planar printing to three-dimensional (3D) structures. Repeatedly stacked fibres formed a micropillar array structure (MPAS) with intervals on the deposition paths by adding carbonyl iron powder particles to a polyethylene oxide (PEO) solution. The growth process of the self-assembled MPAS is documented, and the mechanism of the self-assembled MPAS is proposed. In addition, the effects of substrate speed and injection speed on self-assembly were investigated. Electric field distribution simulations show that the electric field strength around the MPAS is enhanced by nearly ten times so that the micropillar can attract the jet for further deposition. Self-assembly can obtain MPASs with arbitrary paths on different substrates, and the interval of the MPAS can be controlled by using bulging substrates. Furthermore, a self-assembled MPAS has been successfully used to prepare mold cavities, which can be used to prepare MPASs of other materials. Due to their small feature size, large surface area and structural periodicity, micropillar arrays will have promising applications, such as hydrophobicity of surfaces and electrochemical detection. Self-assembly in near-field electrospinning can significantly reduce the preparation cost of an MPAS and provide new processes and ideas.