An optimized influence model of the microchannel plate on the response efficiency of hard X-rays was developed to improve the detection efficiency of hard X-rays. This model incorporates relevant material and structural parameters of the MCP, and further accounts for the crosstalk effects among atomic shells of the substrate material. Based on this model, the influence of key parameters—including substrate material, channel diameter, inter-channel wall thickness, and overall plate thickness—on the detection efficiency was analyzed. Considering current technological constraints, optimal values for these parameters and the corresponding detection efficiency were determined. The results indicate that the detection efficiency for hard X-rays in the 50–200 keV energy range can exceed 45%.