Plasma electrolytic oxidation process is a surface modification technique using plasma-assisted oxidation to prepare the protective layers that improve the surface performances of valve metals such as aluminium, magnesium, and titanium. However, there is poor understanding and ability to control the process, and many uncertainties. The main objective of this paper is to present the discharge behavior with windmill structure, stable group movement and long-term stability. All processes were carried out on 6061 aluminium alloy by applying a bipolar pulsed current with a frequency of 200 Hz, positive and negative pulse durations of 2 ms, and equal pulse pauses. Utilizing current pulses having equal amplitudes between the positive and negative periods resulted in destructive discharges in the late stage. By adjusting the average positive current at a certain time, destructive discharges were eliminated. Meanwhile, various windmill discharge migration patterns were established, in which collective discharges aggregated into several clusters and rotated as a whole on the sample surface. The number of the clusters was correlated to the average positive current. A complete plasma electrolytic oxidation process was proposed to produce a series of coatings, in which the average positive current was reduced at a rate of 0.1 A·min−1 from 95 min to 100 min, and the windmill discharge migration pattern gradually emerged after 100 min. The proposed method increased the treatment duration from ~95 min to ~180 min compared to the process with no current adjustment. In addition, the thickness, relative content of α- and γ-Al2O3 phases, and Vickers hardness of the coatings were significantly enhanced, allowing for the preparation of high-quality coatings.