With soft-core potential model and single electron approximation, the dependence of attosecond pulses on the chirp of the excitation pulse is theoretically investigated by solving 1D time-dependent Schr’dinger equation. The intensity and duration of the attosecond pulses are respectively analyzed. The results show that, instead of producing single attosecond pulse as the unchirped pulse, both the positively and negatively chirped laser pulses will produce attosecond pulse trains. With the increase of the positive chirp of the driving laser pulse , the duration of the attosecond pulse will increase greatly, while the negatively chirped pulse′s effect is little, and some negative chirp can even generate shorter attosecond pulse than that of the zero chirp case.