An electronic system includes a central processing unit (CPU) expansion apparatus and a portable electronic apparatus. The CPU expansion apparatus has a first CPU connector and a first CPU. The portable electronic apparatus has a second CPU connector and a second CPU. When the first CPU connector is connected to the second CPU connector, a data transmission is implemented between the first CPU and the second CPU. A CPU expansion apparatus, portable electronic apparatus and processing method are also disclosed. With the electronic system, CPU expansion apparatus, portable electronic apparatus and processing method according to the invention, the portable electronic apparatus can be connected to an additional CPU externally and is thereby improved in efficiency of processing and computing.
