A pixel arrangement structure, an organic electroluminescent display panel, a metal mask, a display device are provided, the pixel arrangement structure including: first sub-pixels, second sub-pixels and third sub-pixels, all being not overlapped but being spaced apart; one first sub-pixels functions as a central point and other four first sub-pixels function as four vertices to define a first virtual rectangle comprising four second virtual rectangles in a 2×2 matrix in mirror symmetry; the second sub-pixels are at central points of side edges of the first virtual rectangle; two second sub-pixels at central positions of two adjacent side edges of the first virtual rectangle, one first sub-pixel at a vertice of the first virtual rectangle where the two adjacent side edges intersect, and another first sub-pixels at the central point of the first virtual rectangle define four vertices of each second virtual rectangle; the third sub-pixels are within the second virtual rectangles and each is shaped as: a concave polygon, or a closed pattern formed by continuous lines comprising curved lines.