Expansion connector for connecting square tubes

An expansion connector for connecting square tubes, comprising:

• a base and a square column movably connected to the base, wherein
• the square column is movable relatively to an end of the base,
• a first expansion piece and a second expansion piece are sleeved on the square column,
• the first expansion piece has a first insertion groove on a side thereof,
• the first expansion piece has a first insertion piece on one end thereof,
• the first insertion piece has a first bending portion which is in contact with the square column,
• the second expansion piece has a second insertion groove on a side thereof,
• the second expansion piece has a second insertion piece on one end thereof,
• the second insertion piece has a second bending portion which is in contact with the square column,
• the first insertion piece is in detachable engagement with the second insertion groove,
• the second insertion piece is in detachable engagement with the first insertion groove, and
• when the first insertion piece and the second insertion piece respectively abut the second insertion groove and the first insertion groove, each side of the first expansion piece and each side of the second expansion piece are expanded to abut against the inner sides of the square tube.