Abstract: Using the classical ensemble model, the nonsequential double ionization of Xe atoms driven by a few-cycle mid-infrared laser pulse at different carrier-envelop phases (CEP) is systematically studied, and compared with near-infrared laser pulses. The results show that for a mid-infrared laser pulse, with increasing CEP the momentum spectrum of the correlated electrons along the laser polarisation direction changes from the arc-like structure distributed in the first, second and fourth quadrants to the arc-like structure mainly distributed in the first and third quadrants. However, in a near-infrared laser pulse, the momentum spectrum of the correlated electrons changes from being distributed in the first and third quadrants to a V-shaped structure mainly distributed in the first quadrant. The back analysis shows that the NSDI is mainly dominated by the recollision-impact ionisation mechanism in the mid-infrared laser pulse, and the collision time is mainly contributed by the P1 peak near the laser field peak and the P2 peak near the laser field zero. Peak P1 leads to the arc-like structure of the correlated electron momentum spectrum in the first, second and fourth quadrants, P2 leads to the arc-like structure of the correlated electron momentum spectrum in the first and third quadrants. The research shows that for the mid-infrared laser pulse, the NSDI events are further separated according to the time delay between the double ionisation time and the collision time. It is found that even for the recollision-impact ionisation mechanism, the correlation properties of the electron pairs still show different behaviour at different time delay ranges.