In a package process of backside illumination image sensor, a wafer including a plurality of pads is provided. A first carrier is processed to form a plurality of blind vias therein. The first carrier is adhered to the wafer so that the blind vias face to the pads correspondingly. A spacing layer is formed and a plurality of sensing components are disposed. A second carrier is adhered on the spacing layer. Subsequently, a carrier thinning process is performed so that the blind vias become the through holes. An insulating layer is formed on the first carrier. An electrically conductive layer is formed on the insulating layer and filled in the though holes to electrically connect to the pads. The package process can achieve the exact alignment of the through holes and the pads, thereby increasing the package efficiency and improving the package quality.