A method for focusing a fixed-focus photographing module, comprising the following steps: pre-assembling an optical lens assembly to a lens assembly holder, wherein the optical lens assembly is located in a photosensing path of a photosensing component assembled in a circuit board to form a pre-assembled photographing module; performing, by the pre-assembled photographing module, a photographing operation to obtain a testing image; adjusting, according to the testing image, a relative position between the optical lens assembly and the lens assembly holder until the pre-assembled photographing module outputs a clear image as required; and fixing the optical lens assembly and the lens assembly holder to complete a focusing operation and obtain an assembled fixed-focus photographing module; characterized in that, in the step, the optical lens assembly are pre-assembled at a top end of the lens assembly holder, with the optical lens assembly protruding outward from the lens assembly holder and being exposed at an exterior of the lens assembly holder, wherein a glue layer is provided to be disposed or to be formed between the optical lens assembly and the lens assembly holder, for directly packaging the optical lens assembly at the top end of the lens assembly holder, with the glue layer being used to hermetically connect the optical lens assembly and the lens assembly holder, wherein the glue layer is separately formed, wherein the glue layer is in semi-solidified state so that the glue layer has viscosity and the thickness at any position of the glue layer can be adjusted, and after the glue layer is disposed between the optical lens assembly and the lens assembly holder and the focusing of the fixed-focus photographing module is completed, the glue layer is cured in the step, so that the glue layer ensures that the optical lens assembly is held in position after being focused; or a glue is dispensed between the optical lens assembly and the lens assembly holder, wherein the glue is semi-cured to make the semi-cured glue have viscosity and plasticity, and after the lower end surface of the optical lens assembly is mounted on the lens assembly holder and the focusing of the fixed-focus photographing module is completed, the glue is cured in the step, that is, the glue is cured after positions of the optical lens assembly and the lens assembly holder are determined, to form the glue layer sealed between the optical lens assembly and the lens assembly holder. pre-assembling an optical lens assembly to a lens assembly holder, wherein the optical lens assembly is located in a photosensing path of a photosensing component assembled in a circuit board to form a pre-assembled photographing module; performing, by the pre-assembled photographing module, a photographing operation to obtain a testing image; adjusting, according to the testing image, a relative position between the optical lens assembly and the lens assembly holder until the pre-assembled photographing module outputs a clear image as required; and fixing the optical lens assembly and the lens assembly holder to complete a focusing operation and obtain an assembled fixed-focus photographing module; characterized in that, in the step, the optical lens assembly are pre-assembled at a top end of the lens assembly holder, with the optical lens assembly protruding outward from the lens assembly holder and being exposed at an exterior of the lens assembly holder, wherein a glue layer is provided to be disposed or to be formed between the optical lens assembly and the lens assembly holder, for directly packaging the optical lens assembly at the top end of the lens assembly holder, with the glue layer being used to hermetically connect the optical lens assembly and the lens assembly holder, wherein the glue layer is separately formed, wherein the glue layer is in semi-solidified state so that the glue layer has viscosity and the thickness at any position of the glue layer can be adjusted, and after the glue layer is disposed between the optical lens assembly and the lens assembly holder and the focusing of the fixed-focus photographing module is completed, the glue layer is cured in the step, so that the glue layer ensures that the optical lens assembly is held in position after being focused; or a glue is dispensed between the optical lens assembly and the lens assembly holder, wherein the glue is semi-cured to make the semi-cured glue have viscosity and plasticity, and after the lower end surface of the optical lens assembly is mounted on the lens assembly holder and the focusing of the fixed-focus photographing module is completed, the glue is cured in the step, that is, the glue is cured after positions of the optical lens assembly and the lens assembly holder are determined, to form the glue layer sealed between the optical lens assembly and the lens assembly holder.