Abstract: By a classical ensemble method, the influence of pulse duration on sequential double ionization (SDI) of Ar atoms driven by elliptically polarized laser pulse was investigated. The results showed that the doubly charged ion momentum distribution depends strongly on pulse duration. As the pulse duration increases, the ion momentum distribution changes from two-band to four-band structure, and finally to the six-band structure. Back analysis of double ionization trajectories not only manifested the subcycle electron emission in sequential double ionization by elliptically polarized laser pulses，but also showed that the variation of the band structure was originated from the pulse duration dependence of the ionization time of the second electron.