A computer apparatus, a wireless network transmission system and its transmission method are disclosed. The computer apparatus comprises a power supplier, a first circuit architecture, a second circuit architecture and a power controller. A power is provided by the power supplier. The main functionality of the computer apparatus is provided by the first circuit architecture. The second circuit architecture includes a controller, a storage unit and a communication unit. The power controller is electrically connected to the power supplier to provide the power to the first circuit architecture or the second circuit architecture. The first circuit architecture includes the second circuit architecture. The power provided by the power controller is supplied to the first circuit architecture while the computer apparatus is in operating state. The power provided by the power controller is supplied to the second circuit architecture while the computer apparatus is in power-off state. The communication unit is then utilized for wireless transmission.