Fractal dendrites are extensively observed in industry, especially in the electrochemical deposition process. The fractal dendrite electrodeposition behavior of quasi-two-dimensional Cu (Q2D-Cu) metal based on the wire is examined via direct electrodeposition using a thin layer reactor. Here, to explain the fractal growth mechanism, the directional migration and random walking of ions are introduced in the traditional diffusion-limited aggregation model, and fractal patterns consistent with the experimental results are successfully simulated. In addition, the Cu fractal dendrite structure is finely adjusted by varying electrodeposition conditions, demonstrating its great potential for further optimization. The CuO/Q2D-Cu fractal dendrite photothermal device fabricated through in situ assembly of CuO nanowires on Cu fractal dendrite has good photothermal conversion ability. Therefore, metal fractal dendrites, which are considered harmful in the electroplating industry, have application prospects in the photothermal field.