The spatial and temporal distribution of Q-switched diode-pumped solid-state laser (DPSSL) pulses is investigated in multimode regimes. A theory model of spatial and temporal distribution of multimode Qswitched DPSSL pulses is established. The influences of position, initial inversion population density, and mode ratio on pulse width are studied. The results show that the pulse expands in the position wherein two or more mode intensities are equivalent, and the pulse building time difference of the modes are less than one mode pulse width. These results can be applied in pulse compression and mode composition.