Door-opening expander

The utility model provides a door-opening expander which comprises two triangular expanding arms and a hydraulic cylinder, wherein the hydraulic cylinder comprises a fixing sleeve and a piston rod, one end of the piston rod is located in the fixing sleeve, the other end of the piston rod is fixed with a connecting piece, a first angle of each triangular expanding arm is an expanding head, a second angle of each triangular expanding arm is connected with the connecting piece through a pin, and a third angle of each triangular expanding arm is connected with the fixing sleeve through one connecting rod. The door-expanding expander has the advantages that initial expansionary force of the expander is increased, but the size and the weight of the expander are not increased accordingly, and the expander is small, exquisite and light; and the door-expanding expander is simple in structure, convenient to maintain, low in manufacturing cost and the like.