In the "one-point to multiple-points" network laser communication system, in order to reduce the effect of flatness error of mounting surface plane on surface shape accuracy of reflective mirror, make sure the surface shape accuracy of the servo tilt-mirror for the “one-point to multiple-points” network laser communication, the theory analysis of support parameters of integration SiC/Al tilt-mirror was proposed. The effect rule of each parameters on the tilt-mirror surface shape accuracy was analyzed. The support parameters were designed optimally by finite element analysis, and the support point position and the flatness accuracy requirement of the mounting surface plane were defined. The test of surfaces shape accuracy of tilt-mirror using the design parameters after optimation shows that under the premise that the peak and valley (PV) value of the processed surface is better than 53 nm(λ/12), and the root mean square (RMS) value is better than 10 nm(λ/60), with a temperature load of (20±5) ℃, the tilt-mirror is installed, the PV value of the its surface shape accuracy is better than 210 nm(λ/3), and the RMS value is better than 60 nm (λ/10). In addition, the tilt-mirror and the mounting base are made of the same material, which effectively reduces the influence of the temperature change load on the surface shape accuracy. It meets the indicator requirement of servo tilt-mirror surface shape accuracy of the “one-point to multiple-points” network laser communication system.