An innovative bioinspired method is presented for the preparation of surface-modified nanodiamonds (ND) particles by poly(dopamine) (PDA). The process was aimed at improving the thermal conductivity and maintaining the insulating capability of silicone rubber (SiR). ND was successfully and effectively modified by dopamine in different hours, which was confirmed by HR-TEM, TGA, FTIR, and XRD. The poly(dopamine) coating on ND particles improved its interfacial interaction with silicon rubber and promoted the uniform dispersion of fillers, resulting in the ND-18/SiR composite that acquired a higher thermal conductivity (0.295 W/(m·K)) at the loading of 6 wt%, 81 % higher than that of pure silicone rubber (0.163 W/(m·K)). In addition, the composite materials still displayed an excellent insulating property with a resistance of ≈10¹¹ Ω·cm, which was a big advantage for thermal management.