In the experiment of magnetic trapping of neutral atoms, the current noise in the coils will excite the atomic motion, which influences greatly the temperature and the lifetime of the trapped atoms. For anharmonic trap, this excitation has energy-selective characters, and depends on the frequency spectrum of the current noise. The quadrupole trap is chosen as a research object, which is widely used in experiment. The direct simulation Monte Carlo method is used to model the phenomenon of parametric excitation of the atomic motion in the quadrupole trap, and the excitation frequency dependences of the temperature and the trap loss of the atoms are studied. The temperature of the atom cloud is calculated further as the functions of the modulation time and the modulation depth at the two resonant peaks. Furthermore, the influences of the elastic collision rate on the temperature increase of the atom cloud in the process of parametric excitation are also addressed. These results are valuable reference for the experiment of parametric excitation in a quadrupole trap.