The invention discloses a one-side-rotation type arc lock which comprises an adjusting mechanism arranged on a first shell and a tensioning mechanism arranged on a second shell. The adjusting mechanism comprises a radian adjuster rotationally connected with the first shell. The radian adjuster is provided with multiple protrusions in the circumferential direction, wherein the protrusions are used for adjusting the angle between the first shell and the second shell. The protrusions are provided with grooves. The tensioning mechanism comprises adjusting rods which are matched with the grooves for locking the first shell and the second shell. The angle between the first shell and the second shell is adjusted through the radian adjuster rotationally connected with the first shell, and locking of the first shell and the second shell is achieved through the tensioning mechanism. According to the one-side-rotation type arc lock, the structure is simple, operation is convenient, and the angle can be conveniently adjusted.