An electrical system for a mobile power generation device and a mobile power generation device are disclosed. The electrical system includes an electrical cabin and a generator switch cabinet located inside the electrical cabin and including a generator switch device, the generator switch device being configured to connect or disconnect the generator of the mobile power generation device from an external load, the electrical system further includes an auxiliary substation cabinet and an auxiliary substation switch device in the auxiliary substation device cabinet, the auxiliary substation cabinet is located inside the electrical cabin and includes an auxiliary substation device, the auxiliary substation device being configured to convert a first voltage output by the generator into a second voltage; and the auxiliary substation switch device is configured to turn on or turn off the auxiliary substation device, the first voltage being larger than the second voltage.