Abstract: In view of the distribution features of the temperature and density across the different regions of the quiet magnetotail, the same non-uniform distributions of the temperature and density are used as the initial state of the simulation study. In this report, three cases with the different distributions of initial B_y component are investigated. The numerical results illustrate the characteristic evolution of three kinds of magnetic structures. For the varying magnetic field at a given point in the neutral sheet, the hodograms of the typical events are performed. From another point of view, the hodograms of three cases show the features of flux rope structure, plasmoids with Complex closed magnetic field lines and two-dimension "magnetic island", respectively. It was demonstrated from the observations that most plasmoids in the magnetotail are the flux rope structures with a large core field. Monitoring the development of a flux rope structure, the profiles of the directional velocity v_x, v_y, v_z and magnetic field strength B in it as a function of the distance x are given. The computing values of v_x and B are approximately consistent with the observed values in the near and middle tail by Geotail. Moreover, in comparison with Jin et al.’s simulation with a constant initial temperature, in the present work the temperature of plasmoids increases and the density of plasmoids decreases notably, and so the difference between the numerical results and observation is reduced.