An anti-turning umbrella frame comprising a plurality of inner main ribs each of which having an inner end connected to a notch of a shaft, a plurality of middle main ribs, and a plurality of stretchers each of which having an inner end connected to a runner of the shaft; a plurality of inner connecting ribs each of which is arranged between a part of the stretcher close to the outer end of the stretcher and an inner end of the middle main rib; a first rivet point formed by an outer end of the inner main rib being riveted to an inner end of the middle main rib; a second rivet point formed by an outer end of the stretcher being riveted to a middle part of the inner main rib; a third rivet point formed by an inner end of the inner connecting rib being riveted to a part of the stretcher close to the outer end of the stretcher; a fourth rivet point formed by an outer end of the inner connecting rib being riveted to an inner end of the middle main rib; wherein the fourth rivet point is located on an inner side of the first rivet point when the umbrella frame is opened; wherein a positioning portion is disposed on an inner side of the first rivet point of the inner main rib while a locking portion is arranged at the inner connecting rib; the locking portion is corresponding to and matched with the positioning portion; the locking portion and the positioning portion are locked with each other synchronously while the umbrella frame is opened; thus the inner main rib and the middle main rib are connected to form a rigid body for preventing the fourth rivet point from rotating around or pivoting downward with respect to the first rivet point; thereby the middle main rib will not be turned over with respect to the inner main rib. a plurality of inner main ribs each of which having an inner end connected to a notch of a shaft, a plurality of middle main ribs, and a plurality of stretchers each of which having an inner end connected to a runner of the shaft; a plurality of inner connecting ribs each of which is arranged between a part of the stretcher close to the outer end of the stretcher and an inner end of the middle main rib; a first rivet point formed by an outer end of the inner main rib being riveted to an inner end of the middle main rib; a second rivet point formed by an outer end of the stretcher being riveted to a middle part of the inner main rib; a third rivet point formed by an inner end of the inner connecting rib being riveted to a part of the stretcher close to the outer end of the stretcher; a fourth rivet point formed by an outer end of the inner connecting rib being riveted to an inner end of the middle main rib; wherein the fourth rivet point is located on an inner side of the first rivet point when the umbrella frame is opened; wherein a positioning portion is disposed on an inner side of the first rivet point of the inner main rib while a locking portion is arranged at the inner connecting rib; the locking portion is corresponding to and matched with the positioning portion; the locking portion and the positioning portion are locked with each other synchronously while the umbrella frame is opened; thus the inner main rib and the middle main rib are connected to form a rigid body for preventing the fourth rivet point from rotating around or pivoting downward with respect to the first rivet point; thereby the middle main rib will not be turned over with respect to the inner main rib.