A connecting piece (100) comprises a first body (101), two supporting legs (102) respectively connected to the left and right sides of the first body (101), a supporting arm (103) connected to the first body (101) and extends upward; the first body (101) has a first mounting hole (1011) opening forward; the supporting arm (103) has a second mounting hole (1031). It is convenient to assemble and simplifies the connection operation of a cot. A tensioning piece comprises a second body (201), a clamping portion (202), the second body (201) has a connecting hole (2011), the clamping portion (202) has an opening (2021) for clamping onto a side rod (400) of the cot, and the opening (2021) is arc-shaped. So it can be easily disassembled and assembled without additional tools. And a cot is convenient to store and disassemble and assemble.