The impulse aging behavior of the ZnO-Pr6O11-CoO-Cr2O3-Er2O3 varistor ceramics was investigated at the sintering temperature of 1335 degrees-1345 degrees C. Small change in the sintering temperature significantly affected the initial electric field-current density (E-J) characteristics, which decreased from 2878 to 1839 V/cm in the breakdown field and from 70.4 to 48.3 in the nonlinear coefficient. The clamp voltage ratio (V-1200A/V-1mA) for impulse current (1200 A) increased from 2.48 to 2.63 with the increasing sintering temperature. The varistors sintered at 1335 degrees C exhibited the best clamp characteristics. The varistor sintered at 1345 degrees C exhibited the best electrical stability, with %delta E-B=-2.7%, %delta alpha=-11.8%, and %delta J(L)=-6.7% after applying the multi-impulse stress of 1200 A.