The invention relates to a fixed value automatic checking method and device. According to the method, firstly, all fixed value items are subjected to compression coding to reduce data volume; then anencryption algorithm is employed on the compressed data to extract a characteristic value, and it only needs to compare whether a current characteristic value and a standard characteristic value are different to determine whether fixed values are abnormal; and when there is an abnormality, a substation master station system reads a compressed file of the system through a file transfer service of an MMS communication protocol, decoding is performed, and comparison is performed one by one to find an abnormal item. The method has the characteristics of greatly improving the comparison efficiency,reducing a workload, and effectively solving problems that fixed value checking is large in workload, prone to error, and low in efficiency in field work.