A foldable chair, comprising: a foldable chair frame and a chair seat made of a flexible material; the chair frame comprising an X-shaped left support frame, an X-shaped right support frame and a connecting crossbar with two ends connecting the left support frame and the right support frame, the chair seat having a top edge, a bottom edge, and a backside, the chair seat connecting to the chair frame through a plurality of connecting pieces disposed on the top and bottom edges of the backside of the chair seat; each of the left support frame and the right support frame has a detachable pole extending from top to bottom of the chair frame, and the connecting crossbar has two first through holes for the poles to pass through, each of the left support frame and the right support frame has a support tube extending from the bottom edge of the chair seat to the bottom of the chair frame, and correspondingly, the connecting crossbar has two second through holes for the support tubes to pass through, and each of the detachable pole and its corresponding support tube form the X-shaped left support frame or the X-shaped right support frame; wherein the second through holes and the first through holes are distributed inclined in X shape; wherein each of the pole comprises an upper pole body and a lower pole body detachably connected to each other; a hand grip portion is disposed at an upper end of the upper pole body, a leg portion is connected to a lower end of the lower pole body; the upper pole body and the lower pole body are detachably connected through a locking pipe, the lower pole body is inserted into the leg portion and then fixed by a locking sleeve, and the outer end of the connecting crossbar is sleeved on the lower pole body and disposed above the locking sleeve. a foldable chair frame and a chair seat made of a flexible material; the chair frame comprising an X-shaped left support frame, an X-shaped right support frame and a connecting crossbar with two ends connecting the left support frame and the right support frame, the chair seat having a top edge, a bottom edge, and a backside, the chair seat connecting to the chair frame through a plurality of connecting pieces disposed on the top and bottom edges of the backside of the chair seat; each of the left support frame and the right support frame has a detachable pole extending from top to bottom of the chair frame, and the connecting crossbar has two first through holes for the poles to pass through, each of the left support frame and the right support frame has a support tube extending from the bottom edge of the chair seat to the bottom of the chair frame, and correspondingly, the connecting crossbar has two second through holes for the support tubes to pass through, and each of the detachable pole and its corresponding support tube form the X-shaped left support frame or the X-shaped right support frame; wherein the second through holes and the first through holes are distributed inclined in X shape; wherein each of the pole comprises an upper pole body and a lower pole body detachably connected to each other; a hand grip portion is disposed at an upper end of the upper pole body, a leg portion is connected to a lower end of the lower pole body; the upper pole body and the lower pole body are detachably connected through a locking pipe, the lower pole body is inserted into the leg portion and then fixed by a locking sleeve, and the outer end of the connecting crossbar is sleeved on the lower pole body and disposed above the locking sleeve.