the invention relates to an automatic register backup / restore system . the system comprises : a general register file , a backup register file , at least one backup mode signal and at least one selector for selecting the general register file . the general register file comprises a plurality of general registers , and the backup register file comprises a plurality of backup registers . according to the system of the invention , upon exception , a backup mode is determined according to the cause of the exception . then , according to the determined backup mode , the contents of at least one general register are automatically copied into at least one backup register . upon leaving the exception process , according to the determined backup mode , the contents of the corresponding general registers are restored from the corresponding backup registers by using at least one selector . therefore , the system of the invention can reduce the data moving activities between memory and registers during exception process . because of the single operation mode of the system , the system does not need any selection - mode bit for selecting accessible registers due to different operation modes as used in the prior art . therefore , the system of the invention can decrease the latency of accessing registers .