An expandable electronic computing system including an electronic computing system comprising: at least at least a graphics processing unit for generating a PCI-E signal; a signal conversion unit for receiving a PCI-E signal and converting it into a USB signal; a main control unit for driving the signal conversion unit to operate; a USB interface device for receiving the USB signal transmitted by the signal conversion unit, and for transmitting the USB signal to a USB port of an external host through a USB transmission cable. Accordingly, the USB signal generated by one or more electronic computing systems can be transmitted to the external host through the USB port, thereby improving the computing ability of the external host to perform graphics processing tasks or general computing tasks.