Abstract: In order to understand the effect of nuclear motion of H₂⁺ and T⁺ ₂on harmonic intensity and attosecond pulse generation, the intensity changes in the harmonic cutoff region from H₂⁺ and T₂⁺ driven by a 10fs and 20fs lasers were theoretically studied by numerically solving the time-dependent SchrÖdinger equation. The results show that the harmonic intensity follows as H₂⁺ > T₂⁺ under shorter pulse duration case; it follows as T₂⁺ > H₂⁺ under longer pulse duration case. According to the changing law of harmonic intensity, the high intensity and high energy harmonic plateau can be obtained by introducing the half-cycle laser pulse under the optimal harmonic emission intensity, and then the attosecond pulse with pulse duration of 37as can be obtained. The study provides a new way to detect isotopic molecules and generate high intensity and high energy attosecond pulses.