The generation of attosecond(as)pulse can trace the ultrafast electronic dynamics in atoms and molecules with unprecedented accuracy and resolution [1,2].Attosecond pulses can be produced by means of high-order harmonic generation(HHG),which is one of the nonlinear nonperturbative responses of atoms and molecules [3–5].Both experimental and theoretical studies have shown that the HHG spectrum has a general character:It decreases rapidly for the first few harmonics,then exhibits a broad plateau,and finally ends up with a sharp cutoff.