The embodiment of the invention provides an array substrate and a preparation method thereof, and a display device, and relates to the technical field of display so that poor size uniformity of a gap between a source electrode and a drain electrode when barrier layers are formed is prevented and the cost of the barrier layers is reduced and a problem of metal loss and signal discontinuity is solved. The array substrate includes a grid metal layer which is on an underlayer substrate and includes a grid electrode and a grid line; a grid insulating layer; an active layer; a source and drain metal layer which includes the source electrode, the drain electrode, and a data line, wherein the source and drain metal layer includes a copper metal layer and/or a copper alloy layer; and a pixel electrode layer which includes a pixel electrode directly contacting the drain electrode, a first pixel electrode reservation pattern directly contacting the source electrode, and a second pixel electrode reservation pattern directly contacting the data line, wherein an area of the pixel electrode, directly contacting the drain electrode, and the first pixel electrode reservation pattern are located between the active layer and the source and drain metal layer, and an area of the pixel electrode, not directly contacting the drain electrode, and the second pixel electrode reservation pattern are located on/beneath the grid insulating layer. The preparation method is used for preparation of the array substrate.