Flexible microelectrode array (fMEA) is one of the key devices for neural stimulation and recording. For its specific implantation environment, its design and manufacture should meet the requirements of biocompatibility, high resolution, flexibility and low impedance to ensure safe and long-term effective stimulation. In this paper, an fMEA fabrication process was proposed by using flexible polyimide matrix with a variety of 3D platinum nanostructure coatings were fabricated by electrochemical plating at 200 mm stimulation site. Compared with the surface of bare platinum coating, the impedance of 3D micro-structure coating decreased by 94.77% at 1 kHz, reaching 0.824 kΩ and breaking through the limit of 1 kΩ. Compared with other coated electrodes, the CSCc of the novel barrier crystal morphology coated electrodes can be increased by 6.67 times to 13.47 mC cm_^-2. The safe charge injection ability is 19.6 times higher than that of Pt-gray, reaching 2.53 mC cm_^-2. Therefore, this electroplating coating structure and process is promising for effective nerve stimulation/recording in various applications, and have broad application prospects in biomedical fields.