Let G be a semi-direct product of K by A where K and A are both cyclic groups of order n (n e N) and p (p is a prime), respectively. Then we prove that G has an efficient presentation on the minimal ııumber, that is 2, of generators. After ali, as an application of our main result. we give the efficiency of the dihedral group Dln and the metacylic group of order 2m ( m > 4 and m iseven).