The invention discloses a data consistency check method of a heterogeneous system of a cross-network isolation device. The method comprises the following steps: determining to-be-checked equipment types in an I area and an III area according to user needs; respectively extracting to-be-checked static parameters and UID serial numbers corresponding to the to-be-checked equipment types in the I area and the III area according to a check instruction; obtaining binary forms corresponding to the to-be-checked static parameters, respectively calculating the results of the to-be-checked static parameters by using a message digest algorithm, and using the UID serial numbers as corresponding identifiers to obtain to-be-compared data; and transmitting the to-be-compared data of the I area to the III area to be compared with the to-be-compared data of the III area to obtain a consistency check result. On one hand, the UID serial numbers are used as the identifiers to quickly locate the consistency check, in addition, since the message digest algorithm is adopted, the transmission quantity of the to-be-compared data is reduced, therefore the network load is relieved in a data transmission process, and the transmission time is relatively short.