In this paper, a thermally reversible self-healing polysiloxane elastomer based on Diels-Alder (DA) chemistry was successfully prepared via polysiloxane containing maleimide groups and furan rings. The hyperbranched polysiloxane (HPSis) containing furan rings and double bonds was synthesized and introduced to improve the mechanical strength of the polymer. The mechanical strength of polysiloxane without HPSis was only 0.20 MPa; however, it can be increased to 0.87 MPa with the introduction of HPSis. Since HPSis contain multi-furan rings required for thermally reversible reactions, the addition of HPSis would not have a negative effect on self-healing performance. The cracks on the surface of polysiloxane can be self-healed in a short time, and the self-healing efficiency of polysiloxane can achieve 85%. Moreover, flexible conductive composites poly(dimethylsiloxane)/carbon black (PDMS/CB) were fabricated by mixing the polysiloxane matrix with conductive filler carbon black (CB) and can be applied in wearable flexible sensors.