  We employed the new issue of a parton and hadron cascade model PACIAE 2.1 to
systematically investigate the charged particle elliptic flow parameter $v_2$
in the relativistic nuclear collisions at RHIC and LHC energies. With randomly
sampling the transverse momentum $x$ and $y$ components of the particles
generated in string fragmentation on the circumference of an ellipse instead of
circle originally, the calculated charged particle $v_2(\eta)$ and $v_2(p_T)$
fairly reproduce the corresponding experimental data in the Au+Au/Pb+Pb
collisions at $\sqrt{s_{NN}}$=0.2/2.76 TeV. In addition, the charged particle
$v_2(\eta)$ and $v_2(p_T)$ in the p+p collisions at $\sqrt s$=7 TeV as well as
in the p+Au/p+Pb collisions at $\sqrt{s_{NN}}$=0.2/5.02 TeV are predicted.
