In this work, multi-walled carbon nanotubes (CNTs) were noncovalently functionalized with different amount of polymethylphenylsiloxane (PMPS) successfully, and then the products named as PMPS-1/CNTs, PMPS-2/CNTs and PMPS-3/CNTs, respectively, were introduced into silicone rubber (SR) to prepare a series of SR-based composites. Subsequent characterizations were used to analyze the noncovalent functionalization in addition to the thermal oxidative stability and mechanical properties of SR-based composites. The results showed that PMPS was wrapped on CNTs via physical absorption. PMPS/CNTs had good dispersibility in ethanol, and the solutions could remain stable without any visible precipitation even for 6 months. The physical absorption was thought to mainly result from pi-pi stacking, CH-pi interactions and the van der Waals force between PMPS and the sp(2) hybridized network of CNTs. Both the thermal oxidative stability and mechanical properties of PMPS/CNTs/SR composites before and after thermal oxidative aging could be improved by noncovalent functionalization of PMPS. For example, compared with CNTs/SR, the tensile strength before and after thermal oxidative aging of PMPS-2/CNTs/SR could be improved by 13 and 62%, respectively. Moreover, it was found that only the appropriate amount of PMPS can maximize the enhancement of noncovalent functionalization.