A moldboard positioning assembly is adapted for positioning at least two spaced-apart moldboards each having at least one through hole. The moldboard positioning assembly includes a spacer block and two threaded connecting poles. The spacer block is adapted for passing through the through hole of one of the moldboards and is adapted to be disposed between and to abut against the moldboards. The threaded connecting poles respectively project from two opposite ends of the spacer block, and each of the threaded connecting poles is adapted to penetrate through the through hole of a corresponding one of the moldboards. The spacer block has a cross section larger than that of the threaded connecting poles.