The public network communication method of a vehicle-mounted electronic processing unit system described in the present invention divides each functional module in detail according to its functional characteristics and data characteristics through data types, function types, and module numbers, and is the vehicle-mounted electronic processing unit system. Sufficient space is reserved for future development. By extracting the common parts of CAN network and Ethernet, the public network communication method formulated by this patent makes the basic structural content such as the nominal symbol, data type, function type, module number and parameter number of each functional module completely unified, and communicate with each other , so as to realize the data interoperability and resource sharing between the vehicle-mounted electronic processing unit host and each functional module, as well as among the functional modules, and solve the problem that the products in the vehicle-mounted computer system (or vehicle-mounted electronic products) on the market are messy and independent of each other , mutual incompatibility, single function, resources cannot be shared and many other problems.