The invention discloses an image sensor module for a shooting device and an assembly method thereof. The image sensor module for the shooting device comprises a lens assembly containing a lens group, a mainboard, an image sensor chip and a keyset, wherein the mainboard is connected with the image sensor chip through the keyset, and the mainboard and the image sensor chip are electrically communicated through the keyset; the sum of the thickness of the keyset and the thickness of the sensor chip is equal to the focal length of the lens group; the mainboard is provided with a first contact group corresponding to the pin of the image sensor chip; the keyset is provided with a second contact group corresponding to the pin of the image sensor chip; grooves are formed at the positions corresponding to each second contact at the periphery of the keyset; and the inner surfaces of the grooves and regions around the grooves, of the surfaces are respectively provided with an electric conduction plating layer so as to form a third contact group. According to the invention, the technical problems of complicated structure, high cost and poor focusing effect of a focusing device are solved.