To study the characteristics of after-effect parameters of shaped charge jet penetrating finite thickness steel target， the experiments on small shaped charge jet formation and penetration on finite thickness plate with after-effect target were carried out. The numerical simulation on the process of shaped charge jet penetrating finite thickness target plate was carried out by ANSYS/LS-DYNA finite software. The influence of target plate thickness， standoff and after-effect material density on the after-effect parameters of shaped charge jet penetration was analyzed， including the residual jet tip diameter d， tip velocity v and after-effect initiation ability v²d. The results show that with the increase of target thickness， the after-effect initiation ability v²d shows a linear attenuation trend， and around 16% of the initial initiation parameter is lost for every 20 mm increase in thickness. In the range of standoff that the jet keeps continuous， with the increase of standoff， the after-effect initiation ability v²d first increases and then decreases， and its stagnation point appears at the standoff of 8 times the shaped charge diameter. In the range of common explosive density， with the increase of after-effect material density ρ， the attenuation rate of after-effect initiation ability v²d first decreases and then increases. At the same time， there is a stagnation point in the v²d-ρ curve. The peak value of v²d is distributed between ρ=1.6-1.8 g·cm^-3， and the stagnation point position moves to the right with the increase of penetration time.